Once Ibn Sina has laid the foundation of exercise being central to health, he names many exercises as running, swimming, weight lifting, polo, fencing, boxing, wrestling, long jumping, high jumping, etc. He also gives a diet to go along with the exercise:

"The meal should include: (1) meat especially kid of goats; veal, and year - old lambs [this means white meat in today`s terms] (2) wheat, which is cleaned of extraneous matter and gathered during a healthy harvest without ever being exposed to injurious influences (3) sweets (fruits) of appropriate temperament." (Avicenna 1999, p. 390)

Lastly, the third thing mentioned is sleep; to make sure that you do not sleep during the days, and do not stay awake during the nights. From the above reading, it is clear that Ibn Sina gave advice in his book which is still the same advice medical doctors give to their patients. Daily Physical Exercise; and to defeat diseases such as type 2 diabetes, high blood pressure, the prescription of a diet which contains high amounts of Whole Grains and little to no amounts of Refined Carbohydrates.

In The Canon of Medicine, Avicenna described a number of conditions, including melancholia. He described melancholia as a depressive type of mood disorder in which the person may become suspicious and develop certain types of phobias.

Though the threads which comprise Unani healing can be traced all the way back to Galen of Pergamon, who lived in the 2nd century AD, the basic knowledge of Unani medicine as a healing system was developed by Hakim Ibn Sina in his medical encyclopedia The Canon of Medicine. The time of origin is thus dated at circa 1025 AD, when Avicenna wrote The Canon of Medicine in Persia, which remains a text book in the syllabus of Unani medicine in the colleges of India and Pakistan. While he was primarily influenced by Greek and Islamic medicine, he was also influenced by the Indian medical teachings of Sushruta and Charaka.

Ibn Sīnā wrote on Earth sciences such as geology in The Book of Healing. While discussing the formation of mountains, he explained:

Either they are the effects of upheavals of the crust of the earth, such as might occur during a violent earthquake, or they are the effect of water, which, cutting itself a new route, has denuded the valleys, the strata being of different kinds, some soft, some hard... It would require a long period of time for all such changes to be accomplished, during which the mountains themselves might be somewhat diminished in size.

In mechanics, Ibn Sīnā, in The Book of Healing, developed an elaborate theory of motion, in which he made a distinction between the inclination (tendency to motion) and force of a projectile, and concluded that motion was a result of an inclination (mayl) transferred to the projectile by the thrower, and that projectile motion in a vacuum would not cease. He viewed inclination as a permanent force whose effect is dissipated by external forces such as air resistance.

The theory of motion developed by Avicenna may have influenced Jean Buridan's theory of impetus (the ancestor of the inertia and momentum concepts).

In optics, Ibn Sina was among those who argued that light had a speed, observing that "if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite." He also provided a wrong explanation of the rainbow phenomenon. Carl Benjamin Boyer described Avicenna's ("Ibn Sīnā") theory on the rainbow as follows:

Independent observation had demonstrated to him that the bow is not formed in the dark cloud but rather in the very thin mist lying between the cloud and the sun or observer. The cloud, he thought, serves simply as the background of this thin substance, much as a quicksilver lining is placed upon the rear surface of the glass in a mirror. Ibn Sīnā would change the place not only of the bow, but also of the color formation, holding the iridescence to be merely a subjective sensation in the eye.

In 1253, a Latin text entitled Speculum Tripartitum stated the following regarding Avicenna's theory on heat:

Avicenna says in his book of heaven and earth, that heat is generated from motion in external things.

Avicenna's legacy in classical psychology is primarily embodied in the Kitab al-nafs parts of his Kitab al-shifa' (The Book of Healing) and Kitab al-najat (The Book of Deliverance). These were known in Latin under the title De Anima (treatises "on the soul"). The main thesis of these tracts is represented in his so-called "flying man" argument, which resonates with what was centuries later entailed by Descartes's cogito argument (or what phenomenology designates as a form of an "epoche").

Avicenna’s psychology requires that connection between the body and soul be strong enough to ensure the soul’s individuation, but weak enough to allow for its immortality. Avicenna grounds his psychology on physiology, which means his account of the soul is one that deals almost entirely with the natural science of the body and its abilities of perception. Thus, the philosopher's connection between the soul and body is explained almost entirely by his understanding of perception; in this way, bodily perception interrelates with the immaterial human intellect. In sense perception, the perceiver senses the form of the object; first, by perceiving features of the object by our external senses. This sensory information is supplied to the internal senses, which merge all the pieces into a whole, unified conscious experience. This process of perception and abstraction is the nexus of the soul and body, for the material body may only perceive material objects, while the immaterial soul may only receive the immaterial, universal forms. The way the soul and body interact in the final abstraction of the universal from the concrete particular is the key to their relationship and interaction, which takes place in the physical body.

The soul completes the action of intellection by accepting forms that have been abstracted from matter. This process requires a concrete particular (material) to be abstracted into the universal intelligible (immaterial). The material and immaterial interact through the Active Intellect, which is a “divine light” containing the intelligible forms. The Active Intellect reveals the universals concealed in material objects much like the sun makes color available to our eyes.

Ibn Sīnā wrote extensively on early Islamic philosophy, especially the subjects logic, ethics, and metaphysics, including treatises named Logic and Metaphysics. Most of his works were written in Arabic - which was the de facto scientific language of the time in the Middle East, and some were written in the Persian language. Of linguistic significance even to this day are a few books that he wrote in nearly pure Persian language (particularly the Danishnamah-yi 'Ala', Philosophy for Ala' ad-Dawla'). Ibn Sīnā's commentaries on Aristotle often corrected the philosopher, encouraging a lively debate in the spirit of ijtihad.

In the medieval Islamic world, due to Avicenna's successful reconciliation between Aristotelianism and Neoplatonism along with Kalam, Avicennism eventually became the leading school of Islamic philosophy by the 12th century, with Avicenna becoming a central authority on philosophy.

Avicennism was also influential in medieval Europe, particular his doctrines on the nature of the soul and his existence - essence distinction, along with the debates and censure that they raised in scholastic Europe. This was particularly the case in Paris, where Avicennism was later proscribed in 1210. Nevertheless, his psychology and theory of knowledge influenced William of Auvergne, Bishop of Paris, and Albertus Magnus, while his metaphysics had an impact on the thought of Thomas Aquinas.

Early Islamic philosophy and Islamic metaphysics, imbued as it is with Islamic theology, distinguishes more clearly than Aristotelianism the difference between essence and existence. Whereas existence is the domain of the contingent and the accidental, essence endures within a being beyond the accidental. The philosophy of Ibn Sīnā, particularly that part relating to metaphysics, owes much to al-Farabi. The search for a definitive Islamic philosophy separate from Occasionalism can be seen in what is left of his work.

Following al-Farabi's lead, Avicenna initiated a full - fledged inquiry into the question of being, in which he distinguished between essence (Mahiat) and existence (Wujud). He argued that the fact of existence can not be inferred from or accounted for by the essence of existing things, and that form and matter by themselves cannot interact and originate the movement of the universe or the progressive actualization of existing things. Existence must, therefore, be due to an agent - cause that necessitates, imparts, gives, or adds existence to an essence. To do so, the cause must be an existing thing and coexist with its effect.

Avicenna’s consideration of the essence - attributes question may be elucidated in terms of his ontological analysis of the modalities of being; namely impossibility, contingency, and necessity. Avicenna argued that the impossible being is that which cannot exist, while the contingent in itself (mumkin bi-dhatihi) has the potentiality to be or not to be without entailing a contradiction. When actualized, the contingent becomes a ‘necessary existent due to what is other than itself’ (wajib al-wujud bi-ghayrihi). Thus, contingency - in - itself is potential beingness that could eventually be actualized by an external cause other than itself. The metaphysical structures of necessity and contingency are different. Necessary being due to itself (wajib al-wujud bi-dhatihi) is true in itself, while the contingent being is ‘false in itself’ and ‘true due to something else other than itself’. The necessary is the source of its own being without borrowed existence. It is what always exists. The Necessary exists ‘due - to - Its - Self’, and has no quiddity/essence (mahiyya) other than existence (wujud). Furthermore, It is ‘One’ (wahid ahad) since there cannot be more than one ‘Necessary-Existent - due - to - Itself’ without differentia (fasl) to distinguish them from each other. Yet, to require differentia entails that they exist ‘due - to - themselves’ as well as ‘due to what is other than themselves’; and this is contradictory. However, if no differentia distinguishes them from each other, then there is no sense in which these ‘Existents’ are not one and the same. Avicenna adds that the ‘Necessary - Existent - due - to - Itself’ has no genus (jins), nor a definition (hadd), nor a counterpart (nadd), nor an opposite (did), and is detached (bari’) from matter (madda), quality (kayf), quantity (kam), place (ayn), situation (wad’), and time (waqt).

Ibn Sina and Abū Rayhān al-Bīrūnī engaged in a written debate, with Abu Rayhan Biruni mostly criticizing Aristotelian natural philosophy and the Peripatetic school, while Avicenna and his student Ahmad ibn 'Ali al-Ma'sumi respond to Biruni's criticisms in writing. Abu Rayhan began by asking Avicenna eighteen questions, ten of which were criticisms of Aristotle's On the Heavens.

Ibn Sīnā was a devout Muslim and sought to reconcile rational philosophy with Islamic theology. His aim was to prove the existence of God and His creation of the world scientifically and through reason and logic. Avicenna wrote a number of treatises dealing with Islamic theology. These included treatises on the Islamic prophets, whom he viewed as "inspired philosophers", and on various scientific and philosophical interpretations of the Qur'an, such as how Quranic cosmology corresponds to his own philosophical system.

Ibn Sīnā memorized the Qur'an by the age of seven, and as an adult, he wrote five treatises commenting on suras from the Qur'an. One of these texts included the Proof of Prophecies, in which he comments on several Quranic verses and holds the Qur'an in high esteem. Avicenna argued that the Islamic prophets should be considered higher than philosophers.

While he was imprisoned in the castle of Fardajan near Hamadhan, Avicenna wrote his famous "Floating Man" thought experiment to demonstrate human self - awareness and the substantiality and immateriality of the soul. Avicenna believed his "Floating Man" thought experiment demonstrated that the soul is a substance, and claimed humans cannot doubt their own consciousness, even in a situation that prevents all sensory data input. The thought experiment told its readers to imagine themselves created all at once while suspended in the air, isolated from all sensations, which includes no sensory contact with even their own bodies. He argued that, in this scenario, one would still have self - consciousness. Because it is conceivable that a person, suspended in air while cut off from sense experience, would still be capable of determining his own existence, the thought experiment points to the conclusions that the soul is a perfection, independent of the body, and an immaterial substance. The conceivability of this “Floating Man” indicates that the soul is perceived intellectually, which entails the soul’s separateness from the body. Avicenna referred to the living human intelligence, particularly the active intellect, which he believed to be the hypostasis by which God communicates truth to the human mind and imparts order and intelligibility to nature. However, Avicenna posited the brain as the place where reason interacts with sensation. Sensation prepares the soul to receive rational concepts from the universal Agent Intellect. The first knowledge of the flying person would be “I am,” affirming his or her essence. That essence could not be the body, obviously, as the flying person has no sensation. Thus, the knowledge that “I am” is the core of a human being: the soul exists and is self - aware. Avicenna thus concluded that the idea of the self is not logically dependent on any physical thing, and that the soul should not be seen in relative terms, but as a primary given, a substance. The body is unnecessary; in relation to it, the soul is its perfection. In itself, the soul is an immaterial substance.

The practice of judicial astrology was refuted by Avicenna. His reasons were due to the methods used by astrologers in judicial astrology being conjectural rather than empirical and also due to the principles of this type of astrology conflicting with orthodox Islam. He also cited passages from the Qur'an in order to justify his refutation of astrology on both scientific and religious grounds. However, Avicenna’s refutation of astrology (in the treatise titled (Resāla fī ebṭāl aḥkām al-nojūm) concerned only the judicial application of astrology rather than the philosophical principles of the subject and its natural influence. He stated that it was true that each planet had some influence on the earth, but his argument was the difficulty of astrologers being able to determine the exact effect of it. In essence, Avicenna did not refute astrology, but denied man’s limited capacity to be able to know the precise effects of the stars on the sublunar matter. With that, he did not refute the essential dogma of astrology, but only refuted our ability to fully understand it.

In astronomy, he criticized Aristotle's view of the stars receiving their light from the Sun. Ibn Sīnā stated that the stars are self - luminous, and believed that the planets are also self - luminous. He claimed to have observed the transit of Venus across the Sun on May 24, 1032. However, modern scholars have questioned whether he could have observed the transit from his location at that time. He used his transit observation to demonstrate that Venus was, at least sometimes, below the Sun in the Ptolemaic cosmology.

Soon after, he wrote the Compendium of the Almagest, a commentary on Ptolemy's Almagest. Avicenna concluded that Venus is closer to the Earth than the Sun. In 1070, Abu Ubayd al-Juzjani, a pupil of Ibn Sīnā, claimed that his teacher Ibn Sīnā had solved the equant problem in the Ptolemaic model.

Ibn Sīnā used distillation to produce essential oils such as rose essence, forming the foundation of what later became aroma therapy. Four of his works on alchemy were translated into Latin as: Liber Aboali Abincine de Anima in arte Alchemiae, Declaratio Lapis physici Avicennae filio sui Aboali, Avicennae de congelatione et conglutinatione lapidum and Avicennae ad Hasan Regem epistola de Re recta.

In one of these works, Ibn Sīnā discredited the theory of the transmutation of substances commonly believed by alchemists:

Those of the chemical craft know well that no change can be effected in the different species of substances, though they can produce the appearance of such change.

Among his works on alchemy, Liber Aboali Abincine de Anima in arte Alchemiae was the most influential, having influenced later medieval chemists and alchemists such as Vincent of Beauvais.

In another work, translated into Latin as De congelatione et conglutinatione lapidum, Ibn Sina proposed a four - part classification of inorganic bodies, which was a significant improvement over the two - part classification of Aristotle (into orycta and metals) and three - part classification of Galen (into terrae, lapides and metals). The four parts of Ibn Sina's classification were: lapides, sulfur, salts and metals.

Almost half of Ibn Sīnā's works are versified. His poems appear in both Arabic and Persian. As an example, Edward Granville Browne claims that the following Persian verses are incorrectly attributed to Omar Khayyám, and were originally written by Ibn Sīnā:

As early as the 14th century when Dante Alighieri depicted him in Limbo alongside the virtuous non - Christian thinkers in his Divine Comedy such as Virgil, Averroes, Homer, Horace, Ovid, Lucan, Socrates, Plato, and Saladin, Avicenna has been recognized by both East and West, as one of the great figures in intellectual history.

George Sarton, the author of The History of Science, described Ibn Sīnā as "one of the greatest thinkers and medical scholars in history" and called him "the most famous scientist of Islam and one of the most famous of all races, places, and times." He was one of the Islamic world's leading writers in the field of medicine. He was influenced by the approach of Hippocrates and Galen, as well as Sushruta and Charaka. Along with Rhazes, Abulcasis, Ibn al-Nafis, and al-Ibadi, Ibn Sīnā is considered an important compiler of early Muslim medicine. He is remembered in Western history of medicine as a major historical figure who made important contributions to medicine and the European Renaissance. Ibn Sīnā is also considered the father of the fundamental concept of momentum in physics.

In Iran, he is considered a national icon, and is often regarded as one of the greatest Persians to have ever lived. Many portraits and statues remain in Iran today. An impressive monument to the life and works of the man who is known as the 'doctor of doctors' still stands outside the Bukhara museum and his portrait hangs in the Hall of the Avicenna Faculty of Medicine in the University of Paris. There is also a crater on the Moon named Avicenna. Bu-Ali Sina University in Hamadan (Iran), the ibn Sīnā Tajik State Medical University in Dushanbe (The capital of the Republic of Tajikistan), Ibn Sina Academy of Medieval Medicine and Sciences at Aligarh, India, Avicenna School in Karachi and Avicenna Medical College in Lahore, Pakistan, Ibne Sina Balkh Medical School in his native province of Balkh in Afghanistan, Ibni Sina Faculty Of Medicine of Ankara University, Ankara, Turkey, and Ibn Sina Integrated School in Marawi City (Philippines) are all named in his honour. In 1980, the former Soviet Union, which then ruled his birthplace Bukhara, celebrated the thousandth anniversary of Avicenna's birth by circulating various commemorative stamps with artistic illustrations, and by erecting a bust of Avicenna based on anthropological research by Soviet scholars. Near his birthplace in Qishlak Afshona, some 25 km (16 mi). north of Bukhara, a training college for medical staff has been named for him. On the grounds is a museum dedicated to his life, times and work.

In March 2008, it was announced that Avicenna’s name would be used for new Directories of education institutions for health care professionals, worldwide. The Avicenna Directories will list universities and schools where doctors, public health practitioners, pharmacists and others, are educated. The project team stated “Why Avicenna? Avicenna ... was ... noted for his synthesis of knowledge from both east and west. He has had a lasting influence on the development of medicine and health sciences. The use of Avicenna’s name symbolises the worldwide partnership that is needed for the promotion of health services of high quality.”

The treatises of Ibn Sīnā influenced later Muslim thinkers in many areas including theology, philology, mathematics, astronomy, physics, and music. Ibn Sīnā's works numbered almost 450 volumes on a wide range of subjects, of which around 240 have survived. In particular, 150 volumes of his surviving works concentrate on philosophy and 40 of them concentrate on medicine. His most famous works are The Book of Healing, a vast philosophical and scientific encyclopaedia, and The Canon of Medicine.

Ibn Sīnā wrote at least one treatise on alchemy, but several others have been falsely attributed to him. His book on animals was translated by Michael Scot. His Logic, Metaphysics, Physics, and De Caelo, are treatises giving a synoptic view of Aristotelian doctrine, though the Metaphysics demonstrates a significant departure from the brand of Neoplatonism known as Aristotelianism in Ibn Sīnā's world; Arabic philosophers have hinted at the idea that Ibn Sīnā was attempting to "re-Aristotelianise" Muslim philosophy in its entirety, unlike his predecessors, who accepted the conflation of Platonic, Aristotelian, Neo- and Middle - Platonic works transmitted into the Muslim world.

The Logic and Metaphysics have been extensively reprinted, the latter, e.g., at Venice in 1493, 1495, and 1546. Some of his shorter essays on medicine, logic, etc., take a poetical form (the poem on logic was published by Schmoelders in 1836). Two encyclopaedic treatises, dealing with philosophy, are often mentioned. The larger, Al-Shifa' (Sanatio), exists nearly complete in manuscript in the Bodleian Library and elsewhere; part of it on the De Anima appeared at Pavia (1490) as the Liber Sextus Naturalium, and the long account of Ibn Sina's philosophy given by Muhammad al-Shahrastani seems to be mainly an analysis, and in many places a reproduction, of the Al-Shifa'. A shorter form of the work is known as the An-najat (Liberatio). The Latin editions of part of these works have been modified by the corrections which the monastic editors confess that they applied. There is also a حكمت مشرقيه (hikmat - al - mashriqqiyya, in Latin Philosophia Orientalis), mentioned by Roger Bacon, the majority of which is lost in antiquity, which according to Averroes was pantheistic in tone.