• Dominican Priest, Philosopher and Theologian Thomas Aquinas, 1225
• Catholic Friar Francesco di Pietro di Bernardone (St. Francis of Assisi), 1181

Thomas is held in the Roman Catholic Church to be the model teacher for those studying for the priesthood, and indeed the highest expression of both natural reason and speculative theology. The study of his works, according to papal and magisterial documents, is a core of the required program of study for those seeking ordination as priests or deacons, as well as for those in religious formation and for other students of the sacred disciplines (Catholic philosophy, theology, history, liturgy and canon law). The works for which he is best known are the Summa theologiae and the Summa Contra Gentiles. One of the 35 Doctors of the Church, he is considered the Church's greatest theologian and philosopher. Pope Benedict XV declared: "This (Dominican) Order ... acquired new luster when the Church declared the teaching of Thomas to be her own and that Doctor, honored with the special praises of the Pontiffs, the master and patron of Catholic schools."

Thomas was born in Roccasecca, in the Aquino county of the Kingdom of Sicily (present day Lazio region, Italy), circa January 28, 1225. According to some authors, he was born in the castle of his father, Landulf of Aquino. Thomas's father didn’t belong to the most powerful branch of the family and simply held the title miles, while Thomas's mother, Dame Theodora, belonged to the Rossi branch of the Neapolitan Caracciolo family. Landulf's brother Sinibald was abbot of the original Benedictine abbey at Monte Cassino. While the rest of the family's sons pursued military careers, the family intended for Thomas to follow his uncle into the abbacy; this would have been a normal career path for a younger son of southern Italian nobility.

At the age of five, Thomas began his early education at Monte Cassino but after the military conflict that broke out between the Emperor Frederick II and Pope Gregory IX spilled into the abbey in early 1239, Landulf and Theodora had Thomas enrolled at the studium generale (university) recently established by Frederick in Naples. It was here that Thomas was probably introduced to Aristotle, Averroes and Maimonides, all of whom would influence his theological philosophy. It was also during his study at Naples that Thomas came under the influence of John of St. Julian, a Dominican preacher in Naples, who was part of the active effort by the Dominican order to recruit devout followers. There his teacher in arithmetic, geometry, astronomy and music was Petrus de Ibernia.

At age nineteen, Thomas resolved to join the Dominican Order. Thomas's change of heart did not please his family, who had expected him to become a Benedictine monk and perhaps the abbot of the powerful Montecassino Abbey near his family's domains. In an attempt to prevent Theodora's interference in Thomas's choice, the Dominicans arranged for Thomas to be removed to Rome, and from Rome, sent to Paris. However, on his journey to Rome his brothers, per Theodora's instructions, seized him as he was drinking from a spring and took him back to his parents at the castle of Monte San Giovanni Campano.

Thomas was held prisoner for two years in the family castles at Monte San Giovanni and Roccasecca in an attempt to prevent him from assuming the Dominican habit and to push him into renouncing his new aspiration. Political concerns prevented the Pope from ordering Thomas's release, which had the effect of extending Thomas' detention. Thomas passed this time of trial tutoring his sisters and communicating with members of the Dominican Order. Family members became desperate to dissuade Thomas, who remained determined to join the Dominicans. At one point, two of his brothers resorted to the measure of hiring a prostitute to seduce him. According to legend Thomas drove her away wielding a fire iron. That night two angels appeared to him as he slept and strengthened his determination to remain celibate.

By 1244, seeing that all of her attempts to dissuade Thomas had failed, Theodora sought to save the family's dignity, arranging for Thomas to escape at night through his window. In her mind, a secret escape from detention was less damaging than an open surrender to the Dominicans. Thomas was sent first to Naples and then to Rome to meet Johannes von Wildeshausen, the Master General of the Dominican Order.

In 1245, Thomas was sent to study at the University of Paris' Faculty of Arts where he most likely met Dominican scholar Albertus Magnus, then the Chair of Theology at the College of St. James in Paris. When Albertus was sent by his superiors to teach at the new studium generale at Cologne in 1248, Thomas followed him, declining Pope Innocent IV's offer to appoint him abbot of Monte Cassino as a Dominican. Albertus then appointed the reluctant Thomas magister studentium. When Thomas failed his first theological disputation, Albertus prophetically exclaimed: "We call him the dumb ox, but in his teaching he will one day produce such a bellowing that it will be heard throughout the world."

Thomas taught in Cologne as an apprentice professor (baccalaureus biblicus), instructing students on the books of the Old Testament and writing Expositio super Isaiam ad litteram (Literal Commentary on Isaiah), Postilla super Ieremiam (Commentary on Jeremiah) and Postilla super Threnos (Commentary on Lamentations). Then in 1252 he returned to Paris to study for the master's degree in theology. He lectured on the Bible as an apprentice professor, and upon becoming a baccalaureus Sententiarum (bachelor of the Sentences) devoted his final three years of study to commenting on Peter Lombard's Sentences. In the first of his four theological syntheses, Thomas composed a massive commentary on the Sentences entitled Scriptum super libros Sententiarium (Commentary on the Sentences). Aside from his masters writings, he wrote De ente et essentia (On Being and Essence) for his fellow Dominicans in Paris.

In the spring of 1256, Thomas was appointed regent master in theology at Paris and one of his first works upon assuming this office was Contra impugnantes Dei cultum et religionem (Against Those Who Assail the Worship of God and Religion), defending the mendicant orders which had come under attack by William of Saint-Amour. During his tenure from 1256 to 1259, Thomas wrote numerous works, including: Questiones disputatae de veritate (Disputed Questions on Truth), a collection of twenty-nine disputed questions on aspects of faith and the human condition prepared for the public university debates he presided over on Lent and Advent; Quaestiones quodlibetales (Quodlibetal Questions), a collection of his responses to questions posed to him by the academic audience; and both Expositio super librum Boethii De trinitate (Commentary on Boethius's De trinitate) and Expositio super librum Boethii De hebdomadibus (Commentary on Boethius's De hebdomadibus), commentaries on the works of 6th century philosopher Anicius Manlius Severinus Boethius. By the end of his regency, Thomas was working on one of his most famous works, Summa contra Gentiles.

In 1259 Thomas completed his first regency at the studium generale and left Paris so that others in his order could gain this teaching experience. He returned to Naples where he was appointed as general preacher by the provincial chapter of September 29, 1260. In September 1261 he was called to Orvieto as conventual lector responsible for the pastoral formation of the friars unable to attend a studium generale. In Orvieto Thomas completed his Summa contra Gentiles, wrote the Catena aurea, (The Golden Chain), and produced works for Pope Urban IV such as the liturgy for the newly created feast of Corpus Christi and the Contra errores graecorum (Against the Errors of the Greeks).

In February 1265 the newly elected Pope Clement IV summoned Aquinas to Rome to serve as papal theologian. This same year he was ordered by the Dominican Chapter of Agnani to teach at the studium conventuale at the Roman convent of Santa Sabina which had been founded some years before in 1222. The studium at Santa Sabina now became an experiment for the Dominicans, the Order's first studium provinciale, an intermediate school between the studium conventuale and the studium generale. "Prior to this time the Roman Province had offered no specialized education of any sort, no arts, no philosophy; only simple convent schools, with their basic courses in theology for resident friars, were functioning in Tuscany and the meridionale during the first several decades of the order's life. But the new studium at Santa Sabina was to be a school for the province," a studium provinciale. Tolomeo da Lucca, an associate and early biographer of Aquinas, tells us that at the Santa Sabina studium Aquinas taught the full range of philosophical subjects, both moral and natural.

While at the Santa Sabina studium provinciale Thomas began his most famous work the Summa theologiae, which he conceived of specifically as suited to beginning students: "Because a doctor of catholic truth ought not only to teach the proficient, but to him pertains also to instruct beginners. as the Apostle says in 1 Corinthians 3: 1-2, as to infants in Christ, I gave you milk to drink, not meat, our proposed intention in this work is to convey those things that pertain to the Christian religion, in a way that is fitting to the instruction of beginners." While there he also wrote a variety of other works like his unfinished Compendium Theologiae and Responsio ad fr. Ioannem Vercellensem de articulis 108 sumptis ex opere Petri de Tarentasia (Reply to Brother John of Vercelli Regarding 108 Articles Drawn from the Work of Peter of Tarentaise). In his position as head of the studium Aquinas conducted a series of important disputations on the power of God, which he compiled into his De potentia. Nicholas Brunacci [1240 - 1322] was among Aquinas' students at the Santa Sabina studium provinciale and later at the Paris studium generale. In November 1268 he was with Aquinas and his associate and secretary Reginald of Piperno, as they left Viterbo on their way to Paris to begin the academic year. Another student of Aquinas' at the Santa Sabina studium provinciale was Blessed Tommasello da Perugia.

Aquinas remained at the studium at Santa Sabina from 1265 until he was called back to Paris in 1268 for a second teaching regency. With his departure for Paris in 1268 and the passage of time the pedagogical activities of the studium provinciale at Santa Sabina were divided between two campuses. A new convent of the Order at the Church of Santa Maria sopra Minerva had a modest beginning in 1255 as a community for women converts, but grew rapidly in size and importance after being given over to the Dominicans friars in 1275. In 1288 the theology component of the provincial curriculum for the education of the friars was relocated from the Santa Sabina studium provinciale to the studium conventuale at Santa Maria sopra Minerva which was redesignated as a studium particularis theologiae. This studium was transformed in the 16th century into the College of Saint Thomas (Latin: Collegium Divi Thomæ). In the 20th century the college was relocated to the convent of Saints Dominic and Sixtus and was transformed into the Pontifical University of Saint Thomas Aquinas, Angelicum.

In 1268 the Dominican Order assigned Thomas to be regent master at the University of Paris for a second time, a position he held until the spring of 1272. Part of the reason for this sudden reassignment appears to have arisen from the rise of "Averroism" or "radical Aristotelianism" in the universities. In response to these perceived evils, Thomas wrote two works, one of them being De unitate intellectus, contra Averroistas (On the Unity of Intellect, against the Averroists) in which he blasts Averroism as incompatible with Christian doctrine. During his second regency, he finished the second part of the Summa and wrote De virtutibus and De aeternitate mundi, the latter of which dealt with controversial Averroist and Aristotelian beginninglessness of the world. Disputes with some important Franciscans such as Bonaventure and John Peckham conspired to make his second regency much more difficult and troubled than the first. A year before Thomas re-assumed the regency at the 1266 - 67 Paris disputations, Franciscan master William of Baglione accused Thomas of encouraging Averroists, calling him the "blind leader of the blind". Thomas called these individuals the murmurantes (Grumblers). In reality, Thomas was deeply disturbed by the spread of Averroism and was angered when he discovered Siger of Brabant teaching Averroistic interpretations of Aristotle to Parisian students. On 10 December 1270, the bishop of Paris, Etienne Tempier, issued an edict condemning thirteen Aristotlelian and Averroistic propositions as heretical and excommunicating anyone who continued to support them. Many in the ecclesiastical community, the so-called Augustinians, were fearful that this introduction of Aristotelianism and the more extreme Averroism might somehow contaminate the purity of the Christian faith. In what appears to be an attempt to counteract the growing fear of Aristotelian thought, Thomas conducted a series of disputations between 1270 and 1272: De virtutibus in communi (On Virtues in General), De virtutibus cardinalibus (On Cardinal Virtues), De spe (On Hope).

In 1272 Thomas took leave from the University of Paris when the Dominicans from his home province called upon him to establish a studium generale wherever he liked and staff it as he pleased. He chose to establish the institution in Naples, and moved there to take his post as regent master. He took his time at Naples to work on the third part of the Summa while giving lectures on various religious topics. On 6 December 1273 at the Dominican convent of Naples in the Chapel of Saint Nicholas after Matins Thomas lingered and was seen by the sacristan Domenic of Caserta to be levitating in prayer with tears before an icon of the crucified Christ. Christ said to Thomas, "You have written well of me, Thomas. What reward would you have for your labor?" Thomas responded, "Nothing but you Lord." After this exchange something happened, but Thomas never spoke of it or wrote it down. Because of what he saw, he abandoned his routine and refused to dictate to his socius Reginald of Piperno. When Reginald begged him to get back to work, Thomas replied: “Reginald, I cannot, because all that I have written seems like straw to me” (mihi videtur ut palea). What exactly triggered Thomas's change in behavior is believed by Catholics to have been some kind of supernatural experience of God. After taking to his bed, he did recover some strength.

In 1054, a long lasting schism had occurred between the Catholic Church and the churches in communion with the Patriarch of Constantinople, later known as the Eastern Orthodox. Looking to find a way to reunite the Eastern Orthodox churches with the Catholic Church Pope Gregory X convened the Second Council of Lyon to be held on 1 May 1274 and summoned Thomas to attend. At the meeting, Thomas's work for Pope Urban IV concerning the Greeks, Contra errores graecorum, was to be presented. On his way to the Council, riding on a donkey along the Appian Way, he struck his head on the branch of a fallen tree and became seriously ill again. He was then quickly escorted to Monte Cassino to convalesce. After resting for a while, he set out again, but stopped at the Cistercian Fossanova Abbey after again falling ill. The monks nursed him for several days, and as he received his last rites he prayed: "I receive Thee, ransom of my soul. For love of Thee have I studied and kept vigil, toiled, preached and taught...." He died on 7 March 1274 while giving commentary on the Song of Songs.

In 1277 Etienne Tempier, the same bishop of Paris who had issued the condemnation of 1270, issued another more extensive condemnation. One aim of this condemnation was to clarify that God's absolute power transcended any principles of logic that Aristotle or Averroes might place on it. More specifically, it contained a list of 219 propositions that the bishop had determined to violate the omnipotence of God, and included in this list were twenty Thomistic propositions. Their inclusion badly damaged Thomas's reputation for many years.

In The Divine Comedy, Dante sees the glorified soul of Thomas in the Heaven of the Sun with the other great exemplars of religious wisdom. Dante asserts that Thomas died by poisoning, on the order of Charles of Anjou; Villani (ix. 218) cites this belief, and the Anonimo Fiorentino describes the crime and its motive. But the historian Ludovico Antonio Muratori reproduces the account made by one of Thomas's friends, and this version of the story gives no hint of foul play.

Thomas's theology had begun its rise to prestige. Two centuries later, in 1567, Pope Pius V proclaimed St. Thomas Aquinas a Doctor of the Church and ranked his feast with those of the four great Latin fathers: Ambrose, Augustine of Hippo, Jerome, and Gregory. However, in the same period the Council of Trent still turned to Duns Scotus before Thomas as a source of arguments in defense of the Church. Even though Duns Scotus was more consulted at the Council of Trent, Thomas had the honor of having his Summa theologiae placed on the altar alongside the Bible and the Decretals.

In his encyclical of 4 August 1879, Pope Leo XIII stated that Thomas's theology was a definitive exposition of Catholic doctrine. Thus, he directed the clergy to take the teachings of Thomas as the basis of their theological positions. Leo XIII also decreed that all Catholic seminaries and universities must teach Thomas's doctrines, and where Thomas did not speak on a topic, the teachers were "urged to teach conclusions that were reconcilable with his thinking." In 1880, Saint Thomas Aquinas was declared patron of all Catholic educational establishments.

When the devil's advocate at his canonization process objected that there were no miracles, one of the cardinals answered, "Tot miraculis, quot articulis" — "there are as many miracles (in his life) as articles (in his Summa)," viz., thousands. Fifty years after the death of Thomas, on 18 July 1323, Pope John XXII, seated in Avignon, pronounced Thomas a saint.

In a monastery at Naples, near the cathedral of St. Januarius, a cell in which he supposedly lived is still shown to visitors. His remains were placed in the Church of the Jacobins in Toulouse in 1369. Between 1789 and 1974, they were held in Basilique de Saint - Sernin, Toulouse. In 1974, they were returned to the Church of the Jacobins, where they have remained ever since.

In the General Roman Calendar of 1962, in the Roman Catholic Church, Thomas was commemorated on 7 March, the day of death. However, in the General Roman Calendar of 1969, Thomas's memorial was transferred to 28 January, the date of the translation of his relics to Toulouse.

Saint Thomas Aquinas is honored with a feast day in the liturgical year of the Episcopal Church in the United States of America on 28 January.

Thomas was a theologian and a Scholastic philosopher. However, he never considered himself a philosopher, and criticized philosophers, whom he saw as pagans, for always "falling short of the true and proper wisdom to be found in Christian revelation." With this in mind, Thomas did have respect for Aristotle, so much so that in the Summa, he often cites Aristotle simply as "the Philosopher." Much of his work bears upon philosophical topics, and in this sense may be characterized as philosophical. Thomas's philosophical thought has exerted enormous influence on subsequent Christian theology, especially that of the Roman Catholic Church, extending to Western philosophy in general. Thomas stands as a vehicle and modifier of Aristotelianism and Neoplatonism.

Thomas wrote several important commentaries on Aristotle's works, including On the Soul, Nicomachean Ethics and Metaphysics. His work is associated with William of Moerbeke's translations of Aristotle from Greek into Latin.
Thomas believed "that for the knowledge of any truth whatsoever man needs divine help, that the intellect may be moved by God to its act." However, he believed that human beings have the natural capacity to know many things without special divine revelation, even though such revelation occurs from time to time, "especially in regard to such (truths) as pertain to faith." But this is the light that is given to man by God according to man's nature: "Now every form bestowed on created things by God has power for a determined act[uality], which it can bring about in proportion to its own proper endowment; and beyond which it is powerless, except by a superadded form, as water can only heat when heated by the fire. And thus the human understanding has a form, viz. intelligible light, which of itself is sufficient for knowing certain intelligible things, viz. those we can come to know through the senses. "

Thomas's ethics are based on the concept of "first principles of action." In his Summa theologiae, he wrote:

Virtue denotes a certain perfection of a power. Now a thing's perfection is considered chiefly in regard to its end. But the end of power is act. Wherefore power is said to be perfect, according as it is determinate to its act.

Thomas defined the four cardinal virtues as prudence, temperance, justice, and fortitude. The cardinal virtues are natural and revealed in nature, and they are binding on everyone. There are, however, three theological virtues: faith, hope, and charity. These are somewhat supernatural and are distinct from other virtues in their object, namely, God:

Now the object of the theological virtues is God Himself, Who is the last end of all, as surpassing the knowledge of our reason. On the other hand, the object of the intellectual and moral virtues is something comprehensible to human reason. Wherefore the theological virtues are specifically distinct from the moral and intellectual virtues.

Furthermore, Thomas distinguished four kinds of law: eternal, natural, human, and divine. Eternal law is the decree of God that governs all creation. Natural law is the human "participation" in the eternal law and is discovered by reason. Natural law, of course, is based on "first principles":

. . . this is the first precept of the law, that good is to be done and promoted, and evil is to be avoided. All other precepts of the natural law are based on this . . .

The desires to live and to procreate are counted by Thomas among those basic (natural) human values on which all human values are based. According to Thomas, all human tendencies are geared towards real human goods. In this case, the human nature in question is marriage, the total gift of oneself to another that ensures a family for children and a future for mankind. To clarify for Christian believers, Thomas defined love as "to will the good of another."

Human law is positive law: the natural law applied by governments to societies. Divine law is the specially revealed law in the scriptures.

Thomas also greatly influenced Catholic understandings of mortal and venial sins.

Thomas denied that human beings have any duty of charity to animals because they are not persons. Otherwise, it would be unlawful to use them for food. But this does not give humans the license to be cruel to them, for "cruel habits might carry over into our treatment of human beings."

Thomas contributed to economic thought as an aspect of ethics and justice. He dealt with the concept of a just price, normally its market price or a regulated price sufficient to cover seller costs of production. He argued it was immoral for sellers to raise their prices simply because buyers were in pressing need for a product.

The pioneer of neurodynamics, cognitive neuroscientist Walter Freeman, considers the work of Thomas important in remodeling intentionality, the directedness of the mind toward what it is aware of.

Aquinas maintains that a human is a single material substance. He understands the soul as the form of the body, which makes a human being the composite of the two. Thus, only living, form - matter composites can truly be called human; dead bodies are “human” only analogously. One actually existing substance comes from body and soul. A human is a single material substance, but still should be understood as having an immaterial soul, which continues after bodily death.

Ultimately, humans are animals; the animal genus is body; body is material substance. When embodied, a human person is an “individual substance in the category rational animal.” The body belongs to the essence of a human being. In his Summa theologiae Aquinas clearly states his position on the nature of the soul; defining it as “the first principle of life.” The soul is not corporeal, or a body; it is the act of a body. Because the intellect is incorporeal, it does not use the bodily organs, as “the operation of anything follows the mode of its being.”

The human soul is perfected in the body, but does not depend on the body, because part of its nature is spiritual. In this way, the soul differs from other forms, which are only found in matter, and thus depend on matter. The soul, as form of the body, does not depend on matter in this way.

The soul is not matter, not even incorporeal or spiritual matter. If it were, it would not be able to understand universals, which are immaterial. A receiver receives things according to the receiver’s own nature, so in order for soul (receiver) to understand (receive) universals, it must have the same nature as universals. Yet, any substance that understands universals may not be a matter - form composite. So, humans have rational souls which are abstract forms independent of the body. But a human being is one existing, single material substance which comes from body and soul: that is what Thomas means when he writes that “something one in nature can be formed from an intellectual substance and a body,” and “a thing one in nature does not result from two permanent entities unless one has the character of substantial form and the other of matter.”

The soul is a "substantial form"; it is a part of a substance, but it is not a substance by itself. Nevertheless, the soul exists separately from the body, and continues, after death, in many of the capacities we think of as human. Substantial form is what makes a thing a member of the species to which it belongs, and substantial form is also the structure or configuration that provides the object with the abilities that make the object what it is. For humans, those abilities are those of the rational animal.

These distinctions can be better understood in the light of Aquinas’ understanding of matter and form, a hylomorphic ("matter / form") theory derived from Aristotle. In any given substance, matter and form are necessarily united, and each is a necessary aspect of that substance. However, they are conceptually separable. Matter represents what is changeable about the substance – what is potentially something else. For example, bronze matter is potentially a statue, or also potentially a cymbal. Matter must be understood as the matter of something. In contrast, form is what determines some particular chunk of matter to be a specific substance and no other. When Aquinas says that the human body is only partly composed of matter, he means the material body is only potentially a human being. The soul is what actualizes that potential into an existing human being. Consequently, the fact that a human body is live human tissue entails that a human soul is wholly present in each part of the human.

Thomas viewed theology, or the sacred doctrine, as a science, the raw material data of which consists of written scripture and the tradition of the Catholic Church. These sources of data were produced by the self-revelation of God to individuals and groups of people throughout history. Faith and reason, while distinct but related, are the two primary tools for processing the data of theology. Thomas believed both were necessary — or, rather, that the confluence of both was necessary — for one to obtain true knowledge of God. Thomas blended Greek philosophy and Christian doctrine by suggesting that rational thinking and the study of nature, like revelation, were valid ways to understand truths pertaining to God. According to Thomas, God reveals himself through nature, so to study nature is to study God. The ultimate goals of theology, in Thomas's mind, are to use reason to grasp the truth about God and to experience salvation through that truth.

Thomas believed that truth is known through reason (natural revelation) and faith (supernatural revelation). Supernatural revelation has its origin in the inspiration of the Holy Spirit and is made available through the teaching of the prophets, summed up in Holy Scripture, and transmitted by the Magisterium, the sum of which is called "Tradition". Natural revelation is the truth available to all people through their human nature and powers of reason. For example, he felt this applied to rational ways to know the existence of God.

Though one may deduce the existence of God and his Attributes (Unity, Truth, Goodness, Power, Knowledge) through reason, certain specifics may be known only through the special revelation of God in Jesus Christ. The major theological components of Christianity, such as the Trinity and the Incarnation, are revealed in the teachings of the Church and the Scriptures and may not otherwise be deduced.

Faith and reason complement rather than contradict each other, each giving different views of the same Truth.

As a Catholic, Thomas believed that God is the "maker of heaven and earth, of all that is visible and invisible." Like Aristotle, Thomas posited that life could form from non-living material or plant life, a theory of ongoing abiogenesis known as spontaneous generation:

Since the generation of one thing is the corruption of another, it was not incompatible with the first formation of things, that from the corruption of the less perfect the more perfect should be generated. Hence animals generated from the corruption of inanimate things, or of plants, may have been generated then.

Additionally, Thomas considered Empedocles' theory that various mutated species emerged at the dawn of Creation. Thomas reasoned that these species were generated through mutations in animal sperm, and argued that they were not unintended by nature; rather, such species were simply not intended for perpetual existence. That discussion is found in his commentary on Aristotle's Physics:

The same thing is true of those substances which Empedocles said were produced at the beginning of the world, such as the ‘ox-progeny’, i.e., half ox and half man. For if such things were not able to arrive at some end and final state of nature so that they would be preserved in existence, this was not because nature did not intend this [a final state], but because they were not capable of being preserved. For they were not generated according to nature, but by the corruption of some natural principle, as it now also happens that some monstrous offspring are generated because of the corruption of seed.

Augustine of Hippo agreed strongly with the conventional wisdom of his time, that Christians should be pacifists philosophically, but that they should use defense as a means of preserving peace in the long run. For example, he routinely argued that pacifism did not prevent the defense of innocents. In essence, the pursuit of peace might require fighting to preserve it in the long term. Such a war must not be preemptive, but defensive, to restore peace.

Thomas Aquinas, centuries later, used the authority of Augustine's arguments in an attempt to define the conditions under which a war could be just. He laid these out in his historic work, Summa Theologica:

• First, war must occur for a good and just purpose rather than the pursuit of wealth or power.
• Second, just war must be waged by a properly instituted authority such as the state.
• Third, peace must be a central motive even in the midst of violence.

The School of Salamanca expanded Aquinas' understanding of natural law and just war. Given that war is one of the worst evils suffered by mankind, the adherents of the School reasoned that it ought to be resorted to only when it was necessary to prevent an even greater evil. A diplomatic agreement is preferable, even for the more powerful party, before a war is started. Examples of "just war" are:

• In self defense, as long as there is a reasonable possibility of success. If failure is a foregone conclusion, then it is just a wasteful spilling of blood.
• Preventive war against a tyrant who is about to attack.
• War to punish a guilty enemy.

A war is not legitimate or illegitimate simply based on its original motivation: it must comply with a series of additional requirements:

• The response must be commensurate to the evil; more violence than is strictly necessary would be unjust.
• Governing authorities declare war, but their decision is not sufficient cause to begin a war. If the people oppose a war, then it is illegitimate. The people have a right to depose a government that is waging, or is about to wage, an unjust war.
• Once war has begun, there remain moral limits to action. For example, one may not attack innocents or kill hostages.
• The belligerents must exhaust all options for dialogue and negotiation before undertaking a war; war is only legitimate as a last resort.

Under this doctrine, expansionist wars, wars of pillage, wars to convert infidels or pagans, and wars for glory are all inherently unjust.

Thomas believed that the existence of God is self-evident in itself, but not to us. "Therefore I say that this proposition, "God exists," of itself is self evident, for the predicate is the same as the subject.... Now because we do not know the essence of God, the proposition is not self-evident to us; but needs to be demonstrated by things that are more known to us, though less known in their nature — namely, by effects."

Thomas believed that the existence of God can be proven. In the Summa theologiae, he considered in great detail five arguments for the existence of God, widely known as the quinque viae (Five Ways).

1. Motion: Some things undoubtedly move, though cannot cause their own motion. Since, as Thomas believed, there can be no infinite chain of causes of motion, there must be a First Mover not moved by anything else, and this is what everyone understands by God.
2. Causation: As in the case of motion, nothing can cause itself, and an infinite chain of causation is impossible, so there must be a First Cause, called God.
3. Existence of necessary and the unnecessary: Our experience includes things certainly existing but apparently unnecessary. Not everything can be unnecessary, for then once there was nothing and there would still be nothing. Therefore, we are compelled to suppose something that exists necessarily, having this necessity only from itself; in fact itself the cause for other things to exist.
4. Gradation: If we can notice a gradation in things in the sense that some things are more hot, good, etc., there must be a superlative which is the truest and noblest thing, and so most fully existing. This then, we call God -- note Thomas does not ascribe actual qualities to God Himself!
5. Ordered tendencies of nature: A direction of actions to an end is noticed in all bodies following natural laws. Anything without awareness tends to a goal under the guidance of one who is aware. This we call God -- Note that even when we guide objects, in Thomas' view the source of all our knowledge comes from God as well.

Concerning the nature of God, Thomas felt the best approach, commonly called the via negativa, is to consider what God is not. This led him to propose five statements about the divine qualities:

1. God is simple, without composition of parts, such as body and soul, or matter and form.
2. God is perfect, lacking nothing. That is, God is distinguished from other beings on account of God's complete actuality. Thomas defined God as the ‘Ipse Actus Essendi subsistens,’ subsisting act of being.
3. God is infinite. That is, God is not finite in the ways that created beings are physically, intellectually, and emotionally limited. This infinity is to be distinguished from infinity of size and infinity of number.
4. God is immutable, incapable of change on the levels of God's essence and character.
5. God is one, without diversification within God's self. The unity of God is such that God's essence is the same as God's existence. In Thomas's words, "in itself the proposition 'God exists' is necessarily true, for in it subject and predicate are the same."

In this approach, he is following, among others, the Jewish philosopher Maimonides.

Following St. Augustine of Hippo, Thomas defines sin as "a word, deed, or desire, contrary to the eternal law." It is important to note the analogous nature of law in Thomas's legal philosophy. Natural law is an instance or instantiation of eternal law. Because natural law is that which human beings determine according to their own nature (as rational beings), disobeying reason is disobeying natural law and eternal law. Thus eternal law is logically prior to reception of either "natural law" (that determined by reason) or "divine law" (that found in the Old and New Testaments). In other words, God's will extends to both reason and revelation. Sin is abrogating either one's own reason, on the one hand, or revelation on the other, and is synonymous with "evil" (privation of good, or privatio boni). Thomas, like all Scholastics, generally argued that the findings of reason and data of revelation cannot conflict, so both are a guide to God's will for human beings.

Thomas argued that God, while perfectly united, also is perfectly described by Three Interrelated Persons. These three persons (Father, Son and Holy Spirit) are constituted by their relations within the essence of God. Thomas wrote that the term "Trinity" "does not mean the relations themselves of the Persons, but rather the number of persons related to each other; and hence it is that the word in itself does not express regard to another." The Father generates the Son (or the Word) by the relation of self awareness. This eternal generation then produces an eternal Spirit "who enjoys the divine nature as the Love of God, the Love of the Father for the Word."

This Trinity exists independently from the world. It transcends the created world, but the Trinity also decided to give grace to human beings. This takes place through the Incarnation of the Word in the person of Jesus Christ and through the indwelling of the Holy Spirit within those who have experienced salvation by God; according to Aidan Nichols.
Thomas's five proofs for the existence of God take some of Aristotle's assertions concerning principles of being. For Thomas, God as prima causa (first cause) comes from Aristotle's concept of the unmoved mover and asserts that God is the ultimate cause of all things.

In the Summa Theologica, Thomas begins his discussion of Jesus Christ by recounting the biblical story of Adam and Eve and by describing the negative effects of original sin. The purpose of Christ's Incarnation was to restore human nature by removing "the contamination of sin", which humans cannot do by themselves. "Divine Wisdom judged it fitting that God should become man, so that thus one and the same person would be able both to restore man and to offer satisfaction." Thomas argued in favor of the satisfaction view of atonement; that is, that Jesus Christ died "to satisfy for the whole human race, which was sentenced to die on account of sin."

Thomas argued against several specific contemporary and historical theologians who held differing views about Christ. In response to Photinus, Thomas stated that Jesus was truly divine and not simply a human being. Against Nestorius, who suggested that Son of God was merely conjoined to the man Christ, Thomas argued that the fullness of God was an integral part of Christ's existence. However, countering Apollinaris' views, Thomas held that Christ had a truly human (rational) soul, as well. This produced a duality of natures in Christ. Thomas argued against Eutyches that this duality persisted after the Incarnation. Thomas stated that these two natures existed simultaneously yet distinguishably in one real human body, unlike the teachings of Manichaeus and Valentinus.

In short, "Christ had a real body of the same nature of ours, a true rational soul, and, together with these, perfect Deity." Thus, there is both unity (in his one hypostasis) and composition (in his two natures, human and Divine) in Christ.

I answer that, The Person or hypostasis of Christ may be viewed in two ways. First as it is in itself, and thus it is altogether simple, even as the Nature of the Word. Secondly, in the aspect of person or hypostasis to which it belongs to subsist in a nature; and thus the Person of Christ subsists in two natures. Hence though there is one subsisting being in Him, yet there are different aspects of subsistence, and hence He is said to be a composite person, insomuch as one being subsists in two.

Echoing Athanasius of Alexandria, he said that "The only begotten Son of God...assumed our nature, so that he, made man, might make men gods."

In Thomas's thought, the goal of human existence is union and eternal fellowship with God. Specifically, this goal is achieved through the beatific vision, an event in which a person experiences perfect, unending happiness by seeing the very essence of God. This vision, which occurs after death, is a gift from God given to those who have experienced salvation and redemption through Christ while living on earth.

This ultimate goal carries implications for one's present life on earth. Thomas stated that an individual's will must be ordered toward right things, such as charity, peace, and holiness. He sees this as the way to happiness. Thomas orders his treatment of the moral life around the idea of happiness. The relationship between will and goal is antecedent in nature "because rectitude of the will consists in being duly ordered to the last end [that is, the beatific vision]." Those who truly seek to understand and see God will necessarily love what God loves. Such love requires morality and bears fruit in everyday human choices.

Thomas Aquinas belonged to the Dominican Order (formally Ordo Praedicatorum, the Order of Preachers) who began as an order dedicated to the conversion of the Albigensians and other heterodox factions, at first by peaceful means; later the Albigensians were dealt with by means of the Albigensian Crusade. In the Summa theologiae, he wrote:

With regard to heretics two points must be observed: one, on their own side; the other, on the side of the Church. On their own side there is the sin, whereby they deserve not only to be separated from the Church by excommunication, but also to be severed from the world by death. For it is a much graver matter to corrupt the faith which quickens the soul, than to forge money, which supports temporal life. Wherefore if forgers of money and other evil doers are forthwith condemned to death by the secular authority, much more reason is there for heretics, as soon as they are convicted of heresy, to be not only excommunicated but even put to death. On the part of the Church, however, there is mercy which looks to the conversion of the wanderer, wherefore she condemns not at once, but "after the first and second admonition," as the Apostle directs: after that, if he is yet stubborn, the Church no longer hoping for his conversion, looks to the salvation of others, by excommunicating him and separating him from the Church, and furthermore delivers him to the secular tribunal to be exterminated thereby from the world by death.(Summa, II-II, Q.11, art.3.)

Heresy was a capital offense against the secular law of most European countries of the 13th century, which had a limited prison capacity. Simple theft, forgery, fraud, and other such crimes were also capital offenses; Thomas' point seems to be that the gravity of this offense, which touches not only the material goods but also the spiritual goods of others, is at least the same as forgery. Thomas's suggestion specifically demands that heretics be handed to a "secular tribunal" rather than magisterial authority. That Thomas specifically says that heretics "deserve... death" is related to his theology, according to which all sinners have no intrinsic right to life ("For the wages of sin is death; but the free gift of God is eternal life in Christ Jesus our Lord"). Nevertheless, his point is clear: heretics should be executed by the state. He elaborates on his opinion regarding heresy in the next article, when he says:

A grasp of Aquinas's psychology is essential for understanding his beliefs around the afterlife and resurrection. Thomas, following Church doctrine, accepts that the soul continues to exist after the death of the body. Because he accepts that the soul is the form of the body, then he also must believe that the human being, like all material things, is form - matter composite. Substantial form (the human soul) configures prime matter (the physical body) and is the form by which a material composite belongs to that species it does; in the case of human beings, that species is rational animal. So, a human being is a matter - form composite that is organized to be a rational animal. Matter cannot exist without being configured by form, but form can exist without matter — which allows for the separation of soul from body. Aquinas says that the soul shares in the material and spiritual worlds, and so has some features of matter and other, immaterial, features (such as access to universals). The human soul is different from other material and spiritual things; it is created by God, but also only comes into existence in the material body.

Human beings are material, but the human person can survive the death of the body through continued existence of the soul, which persists. The human soul straddles the spiritual and material worlds, and is both a configured subsistent form as well as a configurer of matter into that of a living, bodily human. Because it is spiritual, the human soul does not depend on matter and may exist separately. Because the human being is a soul - matter composite, the body has a part in what it is to be human. Perfected human nature consists in the human dual nature, embodied and intellecting.

Resurrection appears to require dualism, which Thomas rejects. Yet, Aquinas believes the soul persists after the death and corruption of the body, and is capable of existence, separated from the body between the time of death and the resurrection. Aquinas believes in a different sort of dualism, one guided by Christian scripture. Aquinas knows that human beings are essentially physical, but that that physicality has a spirit capable of returning to God after life. For Aquinas, the rewards and punishment of the afterlife are not only spiritual. Because of this, resurrection is an important part of his philosophy on the soul. The human is fulfilled and complete in the body, so the hereafter must take place with souls enmattered in resurrected bodies. In addition to spiritual reward, humans can expect to enjoy material and physical blessings. Because Aquinas’s soul requires a body for its actions, during the afterlife, the soul will also be punished or rewarded in corporeal existence.

Aquinas states clearly his stance on resurrection, and uses it to back up his philosophy of justice; that is, the promise of resurrection compensates Christians who suffered in this world through a heavenly union with the divine. He says, “If there is no resurrection of the dead, it follows that there is no good for human beings other than in this life.” Resurrection provides the impetus for people on earth to give up pleasures in this life. Thomas believes the human who has prepared for the afterlife both morally and intellectually will be rewarded more greatly; however, all reward is through the grace of God. Aquinas insists beatitude will be conferred according to merit, and will render the person better able to conceive the divine. Aquinas accordingly believes punishment is directly related to earthly, living preparation and activity as well. Aquinas’s account of the soul focuses on epistemology and metaphysics, and because of this he believes it gives a clear account of the immaterial nature of the soul. Aquinas conservatively guards Christian doctrine, and thus maintains physical and spiritual reward and punishment after death. By accepting the essentiality of both body and soul, he allows for a heaven and hell described in scripture and church dogma.

Many modern ethicists both within and outside the Catholic Church (notably Philippa Foot and Alasdair MacIntyre) have recently commented on the possible use of Thomas's virtue ethics as a way of avoiding utilitarianism or Kantian "sense of duty" (called deontology). Through the work of twentieth century philosophers such as Elizabeth Anscombe (especially in her book Intention), Thomas's principle of double effect specifically and his theory of intentional activity generally have been influential.

In recent years, the cognitive neuroscientist Walter Freeman proposes that Thomism is the philosophical system explaining cognition that is most compatible with neurodynamics, in a 2008 article in the journal Mind and Matter entitled "Nonlinear Brain Dynamics and Intention According to Aquinas."

Thomas's aesthetic theories, especially the concept of claritas, deeply influenced the literary practice of modernist writer James Joyce, who used to extol Thomas as being second only to Aristotle among Western philosophers. Joyce refers to Aquinas' doctrines in Elementa philosophiae ad mentem D. Thomae Aquinatis doctoris angelici (1898) of Girolamo Maria Mancini, professor of theology at , the Collegium Divi Thomae de Urbe. For example, Mancini's Elementa is referred to in Joyce's early masterpiece Portrait of the Artist as a Young Man.

The influence of Thomas's aesthetics also can be found in the works of the Italian semiotician Umberto Eco, who wrote an essay on aesthetic ideas in Thomas (published in 1956 and republished in 1988 in a revised edition).

Bertrand Russell criticized Aquinas' philosophy on the ground that

He does not, like the Platonic Socrates, set out to follow wherever the argument may lead. He is not engaged in an inquiry, the result of which it is impossible to know in advance. Before he begins to philosophize, he already knows the truth; it is declared in the Catholic faith. If he can find apparently rational arguments for some parts of the faith, so much the better; if he cannot, he need only fall back on revelation. The finding of arguments for a conclusion given in advance is not philosophy, but special pleading. I cannot, therefore, feel that he deserves to be put on a level with the best philosophers either of Greece or of modern times.

This critique is illustrated on the following examples: According to Russell, Aquinas advocates the indissolubility of marriage "on the ground that the father is useful in the education of the children, (a) because he is more rational than the mother, (b) because, being stronger, he is better able to inflict physical punishment." Even though modern approaches to education do not support these views, "no follower of Saint Thomas would, on that account, cease to believe in lifelong monogamy, because the real grounds of belief are not those which are alleged." It may be countered that the treatment of matrimony in the Summa Theologica is in the Supplements volume, which was not written by Aquinas. Moreover, as noted above, Aquinas's introduction of arguments and concepts from the pagan Aristotle and Muslim Averroes was not uncontroversial within the Catholic church.

Aquinas' views of God as first cause, cf. quinque viae, "depend upon the supposed impossibility of a series having no first term. Every mathematician knows that there is no such impossibility; the series of negative integers ending with minus one is an instance to the contrary." Moreover, according to Russell, statements regarding God's essence and existence that are reached within the Aristotelian logic are based on "some kind of syntactical confusion, without which much of the argumentation about God would lose its plausibility."

According to Russell, the methodology of scholasticism used by Thomas is employed for proving what is already believed to be true. Therefore, according to Russell his work should be viewed perhaps as an artful, concise argument, but not a decisive proof. To the contrary, concerning Russell's criticism of Aquinas Anthony Kenny (Aquinas on Mind, 1993, 11) makes the following observation: "It is extraordinary that that accusation should be made by Russell, who in the book Principia Mathematica takes hundreds of pages to prove that two and two make four, which is something he had believed all his life."

For centuries, there have been recurring claims that Thomas had the ability to levitate. For example, G. K. Chesterton wrote that, "His experiences included well attested cases of levitation in ecstasy; and the Blessed Virgin appeared to him, comforting him with the welcome news that he would never be a Bishop."

Francis' father was Pietro Bernardone dei Moriconi, son of Count Domenico Morosini. He lived the high spirited life typical of a wealthy young man, even fighting as a soldier for Assisi. While going off to war in 1204, Francis had a vision that directed him back to Assisi, where he lost his taste for his worldly life. On a pilgrimage to Rome, he joined the poor in begging at St. Peter's Basilica. The experience moved him to live in poverty. Francis returned home, began preaching on the streets, and soon amassed a following. His Order was authorized by Pope Innocent III in 1210. He then founded the Order of Poor Clares, which became an enclosed religious order for women, as well as the Order of Brothers and Sisters of Penance (commonly called the Third Order).

In 1219, he went to Egypt in an attempt to convert the Sultan to put an end to the conflict of the Crusades. By this point, the Franciscan Order had grown to such an extent that its primitive organizational structure was no longer sufficient. He returned to Italy to organize the Order. Once his community was authorized by the Pope, he withdrew increasingly from external affairs. In 1223, Francis arranged for the first Christmas manger scene. In 1224, he received the stigmata, making him the first recorded person to bear the wounds of Christ's Passion. He died during the evening hours of October 3, 1226, while listening to a reading he had requested of Psalm 140.

On July 16, 1228, he was pronounced a saint by Pope Gregory IX. He is known as the patron saint of animals, the environment, and is one of the two patron saints of Italy (with Catherine of Siena). It is customary for Catholic and Anglican churches to hold ceremonies blessing animals on his feast day of October 4. He is also known for his love of the Eucharist, his sorrow during the Stations of the Cross, and for the creation of the Christmas creche or Nativity Scene.

Francis of Assisi was one of seven children born to Pietro, and his wife Pica de Bourlemont, about whom little is known except that she was a noblewoman originally from Provence, France. Pietro was in France on business while Francis was born in Assisi, and Pica had him baptized as Giovanni. When his father returned to Assisi, he took to calling him Francesco ("the Frenchman"), possibly in honour of his commercial success and enthusiasm for all things French. Since the child was renamed in infancy, the change can hardly have had anything to do with his aptitude for learning French, as some have thought.

As a youth, Francesco — or Francis in English — became a devotee of troubadours and was fascinated with all things Transalpine. Although many hagiographers remark about his bright clothing, rich friends, and love of pleasures, his displays of disillusionment toward the world that surrounded him came fairly early in his life, as is shown in the "story of the beggar." In this account, he was selling cloth and velvet in the marketplace on behalf of his father when a beggar came to him and asked for alms. At the conclusion of his business deal, Francis abandoned his wares and ran after the beggar. When he found him, Francis gave the man everything he had in his pockets. His friends quickly chided and mocked him for his act of charity. When he got home, his father scolded him in rage.

In 1201, he joined a military expedition against Perugia and was taken as a prisoner at Collestrada, spending a year as a captive. It is possible that his spiritual conversion was a gradual process rooted in this experience. Upon his return to Assisi in 1203, Francis returned to his carefree life and in 1204, a serious illness led to a spiritual crisis. In 1205, Francis left for Puglia to enlist in the army of the Count of Brienne. A strange vision made him return to Assisi, deepening his ecclesiastical awakening.

According to the hagiographic legend, thereafter he began to avoid the sports and the feasts of his former companions. In response, they asked him laughingly whether he was thinking of marrying, to which he answered, "yes, a fairer bride than any of you have ever seen," meaning his "Lady Poverty". He spent much time in lonely places, asking God for enlightenment. By degrees he took to nursing lepers, the most repulsive victims in the lazar houses near Assisi. After a pilgrimage to Rome, where he joined the poor in begging at the doors of the churches, he said he had a mystical vision of Jesus Christ in the country chapel of San Damiano, just outside of Assisi, in which the Icon of Christ Crucified said to him, "Francis, Francis, go and repair My house which, as you can see, is falling into ruins." He took this to mean the ruined church in which he was presently praying, and so he sold some cloth from his father's store to assist the priest there for this purpose.

His father, Pietro, highly indignant, attempted to change his mind, first with threats and then with beatings. In the midst of legal proceedings before the bishop, Francis renounced his father and his patrimony, laying aside even the garments he had received from him in front of the public. For the next couple of months he lived as a beggar in the region of Assisi. Returning to the countryside around the town for two years, he embraced the life of a penitent, during which he restored several ruined chapels in the countryside around Assisi, among them the Porziuncola, the little chapel of St. Mary of the Angels just outside the town, which later became his favorite abode.

At the end of this period (on February 24, 1209, according to Jordan of Giano), Francis heard a sermon that changed his life forever. The sermon was about Matthew 10:9, in which Christ tells his followers they should go forth and proclaim that the Kingdom of Heaven was upon them, that they should take no money with them, nor even a walking stick or shoes for the road. Francis was inspired to devote himself to a life of poverty.

Clad in a rough garment, barefoot, and, after the Gospel precept, without staff or scrip, he began to preach repentance. He was soon joined by his first follower, a prominent fellow townsman, the jurist Bernardo di Quintavalle, who contributed all that he had to the work. Within a year Francis had eleven followers. Francis chose never to be ordained a priest and the community lived as "lesser brothers," fratres minores in Latin. The brothers lived a simple life in the deserted lazar house of Rivo Torto near Assisi; but they spent much of their time wandering through the mountainous districts of Umbria, always cheerful and full of songs, yet making a deep impression upon their hearers by their earnest exhortations.

Francis' preaching to ordinary people was unusual since he had no license to do so. In 1209 he composed a simple rule for his followers ("friars"), (the Regula primitiva or “Primitive Rule”) which came from verses in the Bible. The rule was “To follow the teachings of our Lord Jesus Christ and to walk in his footsteps.” In 1209, Francis led his first eleven followers to Rome to seek permission from Pope Innocent III to found a new religious Order. Upon entry to Rome, the brothers encountered Bishop Guido of Assisi, who had in his company Giovanni di San Paolo, the Cardinal Bishop of Sabina. The Cardinal, who was the confessor of Pope Innocent III, was immediately sympathetic to Francis and agreed to represent Francis to the pope. Reluctantly, Pope Innocent agreed to meet with Francis and the brothers the next day. After several days, the pope agreed to admit the group informally, adding that when God increased the group in grace and number, they could return for an official admittance. The group was tonsured. This was important in part because it recognized Church authority and prevented his following from possible accusations of heresy, as had happened to the Waldensians decades earlier. Though Pope Innocent initially had his doubts, following a dream in which he saw Francis holding up the Basilica of St. John Lateran (the cathedral of Rome, thus the 'home church' of all Christendom), he decided to endorse Francis' Order. This occurred, according to tradition, on April 16, 1210, and constituted the official founding of the Franciscan Order. The group, then the "Lesser Brothers" (Friars Minor or Franciscan Order), preached on the streets and had no possessions. They were centered in Porziuncola, and preached first in Umbria, before expanding throughout Italy.

From then on, his new Order grew quickly with new vocations. When hearing Francis preaching in the church of San Rufino in Assisi in 1209, Clare of Assisi became deeply touched by his message and she realized her calling. Her cousin Rufino, the only male member of the family in their generation, also joined the new Order.

On the night of Palm Sunday, March 28, 1211, Clare sneaked out of her family's palace. Francis received Clare at the Porziuncola and hereby established the Order of Poor Ladies, later called Poor Clares. This was an Order for women, and he gave a religious habit, or dress, similar to his own to the noblewoman later known as St. Clare of Assisi, before he then lodged her and a few companions in a nearby monastery of Benedictine nuns. Later he transferred them to San Damiano. There they were joined by many other women of Assisi. For those who could not leave their homes, he later formed the Third Order of Brothers and Sisters of Penance. This was a fraternity composed of either laity or clergy whose members neither withdrew from the world nor took religious vows. Instead, they carried out the principles of Franciscan life in their daily lives. Before long this Order grew beyond Italy.

Determined to bring the Gospel to all God’s creatures, Francis sought on several occasions to take his message out of Italy. In the late spring of 1212, he set out for Jerusalem, but he was shipwrecked by a storm on the Dalmatian coast, forcing him to return to Italy. On May 8, 1213, he was given the use of the mountain of La Verna (Alverna) as a gift from Count Orlando di Chiusi, who described it as “eminently suitable for whoever wishes to do penance in a place remote from mankind.” The mountain would become one of his favorite retreats for prayer. In the same year, Francis sailed for Morocco, but this time an illness forced him to break off his journey in Spain. Back in Assisi, several noblemen (among them Tommaso da Celano, who would later write the biography of St. Francis) and some well educated men joined his Order. In 1215, Francis went again to Rome for the Fourth Lateran Council. During this time, he probably met a canon, Dominic de Guzman (later to be Saint Dominic, the founder of the Friars Preachers, another Catholic religious order). In 1217, he offered to go to France. Cardinal Ugolino of Segni (the future Pope Gregory IX), an early and important supporter of Francis, advised him against this and said that he was still needed in Italy.

In 1219, accompanied by another friar and hoping to convert the Sultan of Egypt or win martyrdom in the attempt, Francis went to Egypt where a Crusader army had been encamped for over a year besieging the walled city of Damietta two miles (3.2 kilometers) upstream from the mouth of one of the main channels of the Nile. The Sultan, al-Kamil, a nephew of Saladin, had succeeded his father as Sultan of Egypt in 1218 and was encamped upstream of Damietta, unable to relieve it. A bloody and futile attack on the city was launched by the Christians on August 29, 1219, following which both sides agreed to a ceasefire which lasted four weeks. It was most probably during this interlude that Francis and his companion crossed the Saracen lines and were brought before the Sultan, remaining in his camp for a few days. The visit is reported in contemporary Crusader sources and in the earliest biographies of Francis, but they give no information about what transpired during the encounter beyond noting that the Sultan received Francis graciously and that Francis preached to the Saracens without effect, returning unharmed to the Crusader camp. No contemporary Arab source mentions the visit. One detail, added by Bonaventure in the official life of Francis (written forty years after the event), concerns an alleged challenge by Francis offering trial - by - fire in order to prove the veracity of the Christian Gospel. Although Bonaventure does not suggest as much, subsequent biographies went further, claiming that a fire was kindled which Francis unhesitatingly entered without suffering burns. Such an incident is depicted in the late 13th c. fresco cycle, attributed to Giotto, in the upper basilica at Assisi (see accompanying illustration). According to some late sources, the Sultan gave Francis permission to visit the sacred places in the Holy Land and even to preach there. All that can safely be asserted is that Francis and his companion left the Crusader camp for Acre, from where they embarked for Italy in the latter half of 1220. Drawing on a 1267 sermon by Bonaventure, later sources report that the Sultan secretly converted or accepted a death-bed baptism as a result of the encounter with Francis. The Franciscan Order has been present in the Holy Land almost uninterruptedly since 1217 when Brother Elias arrived at Acre. It received concessions from the Mameluke Sultan in 1333 with regard to certain Holy Places in Jerusalem and Bethlehem, and (so far as concerns the Catholic Church) jurisdictional privileges from Pope Clement VI in 1342.

At Greccio near Assisi, around 1220, Francis celebrated Christmas by setting up the first known presepio or crèche (Nativity scene). His nativity imagery reflected the scene in traditional paintings. He used real animals to create a living scene so that the worshipers could contemplate the birth of the child Jesus in a direct way, making use of the senses, especially sight. Thomas of Celano, a biographer of Francis and Saint Bonaventure both, tell how he only used a straw filled manger (feeding trough) set between a real ox and donkey. According to Thomas, it was beautiful in its simplicity with the manger acting as the altar for the Christmas Mass.

By this time, the growing Order of friars was divided into provinces and groups were sent to France, Germany, Hungary, Spain and to the East. When receiving a report of the martyrdom of five brothers in Morocco, Francis returned to Italy via Venice. Cardinal Ugolino di Conti was then nominated by the Pope as the protector of the Order. The friars in Italy at this time were causing problems, and as such, Francis had to return in order to correct these problems. The Franciscan Order had grown at an unprecedented rate, when compared to prior religious orders. Unfortunately, however, its organizational sophistication had not kept up with this growth and had little more to govern it than Francis' example and simple rule. To address this problem, Francis prepared a new and more detailed Rule, the "First Rule" or "Rule Without a Papal Bull" (Regula prima Regula non bullata) which again asserted devotion to poverty and the apostolic life. However, it introduced greater institutional structure, although this was never officially endorsed by the pope.

On September 29, 1220, Francis handed over the governance of the Order to Brother Peter Catani at the Porziuncola. However, Brother Peter died only five months later, on March 10, 1221, and was buried in the Porziuncola. When numerous miracles were attributed to the deceased brother, people started to flock to the Porziuncola, disturbing the daily life of the Franciscans. Francis then prayed, asking Peter to stop the miracles and to obey in death as he had obeyed during his life. The reports of miracles ceased. Brother Peter was succeeded by Brother Elias as Vicar of Francis. Two years later, Francis modified the "First Rule" (creating the "Second Rule" or "Rule With a Bull"), and Pope Honorius III approved it on November 29, 1223. As the official Rule of the order, it called on the friars "to observe the Holy Gospel of our Lord Jesus Christ, living in obedience without anything of our own and in chastity." In addition, it set regulations for discipline, preaching, and entry into the order. Once the Rule was endorsed by the Pope, Francis withdrew increasingly from external affairs. During 1221 and 1222, Francis crossed Italy, first as far south as Catania in Sicily and afterwards as far north as Bologna.

While he was praying on the mountain of Verna, during a forty day fast in preparation for Michaelmas (September 29), Francis is said to have had a vision on or about September 14, 1224, the Feast of the Exaltation of the Cross, as a result of which he received the stigmata. Brother Leo, who had been with Francis at the time, left a clear and simple account of the event, the first definite account of the phenomenon of stigmata. "Suddenly he saw a vision of a seraph, a six - winged angel on a cross. This angel gave him the gift of the five wounds of Christ." Suffering from these stigmata and from trachoma, Francis received care in several cities (Siena, Cortona, Nocera) to no avail. In the end, he was brought back to a hut next to the Porziuncola. Here, in the place where it all began, feeling the end approaching, he spent the last days of his life dictating his spiritual testament. He died on the evening of October 3, 1226, singing Psalm 142(141) – "Voce mea ad Dominum".

On July 16, 1228, he was pronounced a saint by Pope Gregory IX (the former cardinal Ugolino di Conti, friend of St Francis and Cardinal Protector of the Order). The next day, the Pope laid the foundation stone for the Basilica of Saint Francis in Assisi. He was buried on May 25, 1230, under the Lower Basilica, but his tomb was soon hidden on orders of Brother Elias to protect it from Saracen invaders.. His burial place remained unknown until it was discovered in 1818. Pasquale Belli then constructed for his remains a crypt in neo-classical style in the Lower Basilica. It was refashioned between 1927 and 1930 into its present form by Ugo Tarchi, stripping the wall of its marble decorations. In 1978, the remains of St. Francis were examined and confirmed by a commission of scholars appointed by Pope Paul VI, and put in a glass urn in the ancient stone tomb. Saint Francis is considered the first Italian poet by literary critics. He believed commoners should be able to pray to God in their own language, and he wrote often in the dialect of Umbria instead of Latin. His writings are considered to have great literary and religious value.

It has been argued that no one in history was as dedicated as Francis to imitate the life, and carry out the work of Christ, in Christ’s own way. This is important in understanding Francis' character and his affinity for the Eucharist and respect for the priests who carried out the sacrament. He and his followers celebrated and even venerated poverty. Poverty was so central to his character that in his last written work, the Testament, he said that absolute personal and corporate poverty was the essential lifestyle for the members of his order. He believed that nature itself was the mirror of God. He called all creatures his “brothers” and “sisters,” and even preached to the birds and supposedly persuaded a wolf to stop attacking some locals if they agreed to feed the wolf. In his “Canticle of the Creatures” (“Praises of Creatures” or “Canticle of the Sun”), he mentioned the “Brother Sun” and “Sister Moon,” the wind and water, and “Sister Death.” He referred to his chronic illnesses as his “sisters." His deep sense of brotherhood under God embraced others, and declared that “he considered himself no friend of Christ if he did not cherish those for whom Christ died.” Francis's visit to Egypt and attempted rapprochement with the Muslim world had far-reaching consequences, long past his own death, since after the fall of the Crusader Kingdom it would be the Franciscans, of all Catholics, who would be allowed to stay on in the Holy Land and be recognized as "Custodians of the Holy Land" on behalf of the Catholic Church.

Many of the stories that surround the life of St. Francis deal with his love for animals. Perhaps the most famous incident that illustrates the Saint's humility towards nature is recounted in the "Fioretti" ("Little Flowers"), a collection of legends and folklore that sprang up after the Saint's death. It is said that, one day, while Francis was travelling with some companions, they happened upon a place in the road where birds filled the trees on either side. Francis told his companions to "wait for me while I go to preach to my sisters the birds." The birds surrounded him, intrigued by the power of his voice, and not one of them flew away. He is often portrayed with a bird, typically in his hand.

Another legend from the Fioretti tells that in the city of Gubbio, where Francis lived for some time, was a wolf "terrifying and ferocious, who devoured men as well as animals." Francis had compassion upon the townsfolk, and so he went up into the hills to find the wolf. Soon, fear of the animal had caused all his companions to flee, though the saint pressed on. When he found the wolf, he made the sign of the cross and commanded the wolf to come to him and hurt no one. Miraculously the wolf closed his jaws and lay down at the feet of St. Francis. "Brother Wolf, you do much harm in these parts and you have done great evil," said Francis. "All these people accuse you and curse you... But brother wolf, I would like to make peace between you and the people." Then Francis led the wolf into the town, and surrounded by startled citizens made a pact between them and the wolf. Because the wolf had “done evil out of hunger, the townsfolk were to feed the wolf regularly. In return, the wolf would no longer prey upon them or their flocks. In this manner Gubbio was freed from the menace of the predator. Francis even made a pact on behalf of the town dogs, that they would not bother the wolf again. Finally, to show the townspeople that they would not be harmed, Francis blessed the wolf.

Francis preached the teaching of the Catholic Church, that the world was created good and beautiful by God but suffers a need for redemption because of the primordial sin of man. He preached to man and beast the universal ability and duty of all creatures to praise God (a common theme in the Psalms) and the duty of men to protect and enjoy nature as both the stewards of God's creation and as creatures ourselves.

On November 29, 1979, Pope John Paul II declared St. Francis to be the Patron of Ecology.

Then during the World Environment Day 1982, he said that St. Francis' love and care for creation was a challenge for contemporary Catholics and a reminder "not to behave like dissident predators where nature is concerned, but to assume responsibility for it, taking all care so that everything stays healthy and integrated, so as to offer a welcoming and friendly environment even to those who succeed us." The same Pope wrote on the occasion of the World Day of Peace, January 1, 1990, the saint of Assisi "offers Christians an example of genuine and deep respect for the integrity of creation..." He went on to make the point that St Francis: "As a friend of the poor who was loved by God's creatures, Saint Francis invited all of creation – animals, plants, natural forces, even Brother Sun and Sister Moon – to give honor and praise to the Lord. The poor man of Assisi gives us striking witness that when we are at peace with God we are better able to devote ourselves to building up that peace with all creation which is inseparable from peace among all peoples."

Pope John Paul II concluded that section of the document with these words, "It is my hope that the inspiration of Saint Francis will help us to keep ever alive a sense of 'fraternity' with all those good and beautiful things which Almighty God has created."

Saint Francis's feast day is observed on October 4. A secondary feast in honor of the stigmata received by St Francis, celebrated on September 17, was inserted in the General Roman Calendar in 1585 (later than the Tridentine Calendar) and suppressed in 1604, but was restored in 1615. In the New Roman Missal of 1969, it was removed, as something of a duplication of the main feast on October 4, from the General Calendar and left to the calendars of certain localities and of the Franciscan Order. Wherever the traditional Roman Missal is used, however, the feast of the Stigmata remains in the General Calendar.

On June 18, 1939, Pope Pius XII named Francis a joint Patron Saint of Italy along with Saint Catherine of Siena with the apostolic letter "Licet Commissa", AAS XXXI (1939), 256 - 257. Pope Pius mentioned the two saints in the laudative discourse he pronounced on May 5, 1949, in the Church of Santa Maria sopra Minerva.

St. Francis is honored in the Church of England, the Anglican Church of Canada, the Episcopal Church USA, the Old Catholic Churches, the Evangelical Lutheran Church in America, and other churches and religious communities on October 4. The Evangelical Church in Germany, however, commemorates St. Francis' feast day on his death day, October 3.

On 13 March 2013, Former Cardinal Jorge Mario Bergoglio of Argentina upon his election as Pope chose Francis for his papal name, becoming Pope Francis in honor of Saint Francis of Assisi.