Strindberg and Siri's daughter Karin was born on 26 February 1880. Buoyant from the reception of The Red Room, Strindberg swiftly completed The Secret of the Guild, a historical drama set in Uppsala at the beginning of the 15th century about the conflict between two masons over the completion of the city cathedral, which opened at the Royal Theatre on 3 May 1880 (his first première in nine years); Siri played Margaretha. That spring he formed a friendship with the painter Carl Larsson. A collected edition of all of Strindberg's previous writings was published under the title Spring Harvest. From 1881, at the invitation of Edvard Brandes, Strindberg began to contribute articles to the Morgenbladet, a Copenhagen daily newspaper. In April he began work on The Swedish People, a four - part cultural history of Sweden written as a series of depictions of ordinary people's lives from the 9th century onwards, which he undertook mainly for financial reasons and which absorbed him for the next year; Larsson provided illustrations. At Strindberg's insistence, Siri resigned from the Royal Theatre in the spring, having become pregnant again. Their second daughter, Greta, was born on 9 June 1881, while they were staying on the island of Kymmendö. That month, a collection of essays from the past ten years, Studies in Cultural History, was published. Ludvig Josephson (the new artistic director of Stockholm's New Theatre) agreed to stage Master Olof, eventually opting for the prose version — the five - hour - long production opened on 30 December 1881 under the direction of August Lindberg to favorable reviews. While this production of Master Olaf was his breakthrough in the theater, Strindberg's five - act fairy - tale play Lucky Peter's Journey, which opened on 22 December 1883, brought him his first significant success, although he dismissed it as a potboiler. In March 1882 he wrote in a letter to Josephson: "My interest in the theater, I must frankly state, has but one focus and one goal — my wife's career as an actress"; Josephson duly cast her in two roles the following season.

Having returned to Kymmendö during the summer of 1882, Strindberg wrote a collection of anti - establishment short stories, The New Kingdom. While there, to provide a lead role for his wife and as a reply to Henrik Ibsen's A Doll's House (1879), he also wrote Sir Bengt's Wife, which opened on 25 November 1882 at the New Theatre. He moved to Grez - sur - Loing, just south of Paris, France, where Larsson was staying. He then moved to Paris, which they found noisy and polluted. Income earned from Lucky Peter's Journey enabled him to move to Switzerland in 1883. He resided in Ouchy, where he stayed for some years. On 3 April 1884, Siri gave birth to their son, Hans.

In 1884 Strindberg wrote a collection of short stories, Getting Married, that presented women in an egalitarian light and for which he was tried for and acquitted of blasphemy in Sweden. Two groups "led by influential members of the upper classes, supported by the right - wing press" probably instigated the prosecution; at the time, most people in Stockholm thought that Queen Sophia was behind it. By the end of that year Strindberg was in a despondent mood: "My view now is," he wrote, "everything is shit. No way out. The skein is too tangled to be unraveled. It can only be sheared. The building is too solid to be pulled down. It can only be blown up." In May 1885 he wrote: "I am on my way to becoming an atheist." In the wake of the publication of Getting Married, he began to correspond with Émile Zola. During the summer he completed a sequel volume of stories, though some were quite different in tone from those of the first. Another collection of stories, Utopias in Reality, was published in September 1885, though it was not well received.

In 1885, they moved back to Paris. In September 1887 he began to write a novel in French about his relationship with Siri von Essen called The Confession of a Fool. In 1887, they moved to Issigatsbühl, near Lindau by Lake Constance. His next play, Comrades (1886), was his first in a contemporary setting. After the trial he evaluated his religious beliefs, he concluded he need to leave Lutheranism, which he had been since childhood, and after briefly being a deist, he became an atheist. He needed a credo and he used Jean - Jacques Rousseau nature worshiping as one, which he had studied while a student. His works The People of Hemsö (1887) and Among French Peasants (1889) were influenced by his study of Rousseau. He then moved to Germany, where he fell in love with Chancellor Otto von Bismarck's Prussia status of the officer corps. After that, he grew very critical of Rousseau and turned to Friedrich Nietzsche's philosophies, which emphasized the male intellect. Nietzsche's influence can be seen in The Confession of a Fool (1888), Pariah (1889), Creditors (1889), and By the Open Sea (1890).

Another change in his life after the trial is that Strindberg decided he wanted a scientific life instead of a literary one, and began to write about non - literary subjects. When he was 37, he began The Son of a Servant, a four - part autobiography. The first part ends in 1867, the year he left home for Uppsala. Part two describes his youth up to 1872. Part three, or The Red Room, is when he is a poet and journalist and it ends with him meeting Siri von Essen. Part four, which dealt with the years spanning from 1877 to 1886, was banned by his publishers and was not published until after his death. The three missing years, 1875 – 1877, was the time Strindberg was wooing von Essen and their marriage; entitled He and She, it was not printed until 1919, after his death. It contains the love letters between the two during that period.

In the later half of the 1880s Strindberg discovered Naturalism. After completing The Father in matter of weeks, he sent a copy to Émile Zola for his approval, though his reaction was lukewarm. The drama revolves around the conflict between the Captain, a father, husband, and scientist, and his wife, Laura, over the education of their only child, a fourteen year old daughter named Berta. Through unscrupulous means, Laura gets the Captain to doubt his fatherhood until he suffers a mental and physical collapse. While writing The Father, Strindberg himself was experiencing marital problems and doubted the paternity of his children. He also suspected that Ibsen had based Hjalmar Ekdal in The Wild Duck (1884) on Strindberg because he felt that Ibsen viewed him as a weak and pathetic husband; he reworked the situation of Ibsen's play into a warfare between the two sexes. From November 1887 to April 1889, Strindberg stayed in Copenhagen. While there he had several opportunities to meet with both Georg Brandes and his brother Edvard Brandes. Georg helped him put on The Father, which had its première on 14 November 1887 at the Casino Theatre in Copenhagen. It enjoyed a successful run for eleven days after which it toured the Danish provinces.

Before writing Creditors, Strindberg completed one of his most famous pieces, Miss Julie. He wrote the play with a Parisian stage in mind, in particular the Théâtre Libre, founded in 1887 by Andre Antoine. In the play he used Charles Darwin's theory of survival of the fittest and dramatized a doomed sexual encounter that crosses the division of social classes. As the "son of a servant," it is believed this play was inspired by his marriage to an aristocratic woman.

In the essay On Psychic Murder (1887), he referred to the psychological theories of the Nancy School, which advocated the use of hypnosis. Strindberg developed a theory that sexual warfare was not motivated by carnal desire but by relentless human will. The winner was the one who had the strongest and most unscrupulous mind, someone who, like a hypnotist, could coerce a more impressionable psyche to submission. His view on psychological power struggles may be seen in works such as Creditors (1889), The Stronger (1889), and Pariah (1889).

In 1888, after a separation and reconciliation with Siri von Essen, he founded the Scandinavian Experimental Theatre in Copenhagen, where Siri became manager. He asked writers to send him scripts, which he received from Herman Bang, Gustav Wied and Nathalia Larsen. Less than a year later, with the theater and reconciliation short lived, he moved back to Sweden while Siri moved back to her native Finland with the children. While there, he rode out the final phase of the divorce and later used this agonizing ordeal for the basis of The Bond and the Link (1893). Strindberg also became interested in short drama, called Quart d'heure. He was inspired by writers such as Gustave Guiche and Henri de Lavedan. His notable contribution was The Stronger (1889). As a result of the failure of the Scandinavian Experimental Theatre, Strindberg did not work as a playwright for three years. In 1889, he published an essay entitled "On Modern Drama and the Modern Theatre," in which he disassociated himself from naturalism, arguing that it was petty and unimaginative realism. His sympathy for Nietzsche's philosophy and atheism in general were also on the wane. He entered the period of his "Inferno crisis," in which he had psychological and religious upheavals that influenced his later works.

After his disenchantment with naturalism, Strindberg had a growing interest in transcendental matters. Symbolism was just beginning at this time. Verner von Heidenstam and Ola Hanson had dismissed naturalism as "shoemaker realism" that rendered human experience in simplistic terms. This is believed to have stalled his creativity, and Strindberg insisted he was in a rivalry and forced to defend naturalism, even though he had exhausted its literary potential. These works include: Debit and Credit (1892), Facing Death (1892), Motherly Love (1892), and The First Warning (1893). His play The Keys of Heaven (1892) was inspired by the loss of his children in his divorce. He also completed one of his few comedies, Playing with Fire (1893) and his post - inferno trilogy To Damascus (1898 – 1904).

In 1892, he experienced writer's block, which led to a drastic reduction in his income. Depression followed as he was unable to meet his financial obligations and to support his children and former wife. A fund was set up through an appeal in a German magazine. This money allowed him to leave Sweden and he joined artistic circles in Berlin, Germany. Otto Brahm's Freie Bühne theater premiered some of his famous works in Germany, including The Father, Miss Julie and Creditors.

Similar to twenty years earlier when he frequented The Red Room, he now went to the German tavern The Black Porker. Here he met a diverse group of artists from Scandinavia, Poland, and Germany. His attention turned to Frida Uhl, who was twenty - three years younger than he. They were married in 1893. Less than a year later, their daughter Kerstin was born and the couple separated, though their marriage was not officially dissolved until 1897. Frida's family, in particular her mother, who was a devout Catholic, had an important influence on Strindberg and in an 1894 letter he declared "I feel the hand of our Lord resting over me."

Some critics think that Strindberg suffered from severe paranoia in the mid 1890s, and perhaps that he experienced temporarily insanity. Others, including Evert Sprinchorn and Olof Lagercrantz believed he intentionally turned himself into his own guinea pig by doing psychological and drug induced self - experimentation. He wrote on subjects such as botany, chemistry, and optics before returning to literature with the publication of his edited journals Legends and Jacob Wrestling (both 1898), where he noted the impact Emanuel Swedenborg had on his current work.

"The Powers" were central to Strindberg's later work. He said "the Powers" were an outside force that had caused him his physical and mental suffering because they were acting for retribution to humankind for their wrongdoings. As William Blake, Ralph Waldo Emerson, Honoré de Balzac, and William Butler Yeats had been, he was drawn to Swedenborg's mystical visions, with their depictions of spiritual landscape and Christian morality. Strindberg believed for the rest of his life that the relationship between the transcendental and the real world was described by a series of "correspondences" and that everyday events were really messages from above of which only the enlightened could make sense. He also felt he was chosen by Providence to atone for the moral decay of others and felt his tribulations were payback for misdeeds earlier in his life.

In 1899, he returned to Sweden, following a successful production of Master Olaf in 1897 (which was re-staged in 1899 to mark Strindberg's fiftieth birthday). He had the desire to become the national poet and felt historical dramas were the way to attain that status. Though Strindberg claimed that he was writing "realistically," he freely altered past events and biographical information, and telescoped chronology. Works included the so called Vasa Trilogy: The Saga of the Folkungs (1899), Gustavus Vasa (1899), and Erik XIV (1899).

Strindberg was pivotal in the creation of chamber plays. Max Reinhardt was a big supporter of his, staging some of his plays at the Kleines Theater in 1902 (including The Bond, The Stronger, and The Outlaw). Once Otto Brahm relinquished his role as head as of the Deutsches Theater, Reinhardt took over and produced Strindberg's plays.

In 1903, Strindberg planned to write a grand cycle of plays based on world history, but the idea soon faded. He had completed short plays about Martin Luther, Plato, Moses, Jesus Christ, and Socrates. He wrote another historical drama in 1908 after the Royal Theatre convinced him to put on a new play for its sixtieth birthday. He wrote The Last of the Knights (1908), Earl Birger of Bjalbo (1909), and The Regents (1909).

His other works, such as Days of Loneliness (1903), The Roofing Ceremony (1907), and The Scapegoat (1907), and the novels The Gothic Rooms (1904) and Black Banners, Genre Scenes from the Turn of the Century (1907) have been viewed as precursors to Marcel Proust and Franz Kafka.

August Falck, an actor, wanted to put on a production of Miss Julie and wrote to him for permission. In September 1906 he staged the first Swedish production of Miss Julie. August Palme, Strindberg's friend, played Jean and Manda Bjorling played Julie.

In 1909, Strindberg thought he might get the Nobel Prize in Literature, but instead lost to Selma Lagerlöf, the first woman and first Swede to win the award. The leader of the Social Democrat Youth Alliance started a fund raiser for a special award. Nathan Söderblom was noted as a donor, yet he was criticized by the conservative party. In total there was 45,000 Swedish crowns collected, by more than 20,000 donors, most of whom were workers. Bonnier Group paid him 200,000 Swedish crowns for his complete works. He invited his first three children to Stockholm and divided the money into five shares, one for each child, one for Siri, and the other for himself.

He founded The Intimate Theatre in Stockholm in 1907. His theater was modeled after Max Reinhart's Kammerspiel Haus. Strindberg had the intention of the theater being used for his plays and his plays only, he also had the intention of the theater being used mainly to perform chamber plays. For the theater's opening, Strindberg wrote four chamber plays: Thunder in the Air, The Burned Site, The Ghost Sonata, and The Pelican. Strindberg had very specific ideas about how the theater would be opened and operated. He drafted a series of rules for his theater in a letter to August Falck: 1. No liquor. 2. No Sunday performances. 3. Short performances without intermissions. 4. No calls. 5. Only 160 seats in the auditorium. 6. No prompter. No orchestra, only music on stage. 7. The text will be sold at the box office and in the lobby. 8. Summer performances. Falck helped to design the auditorium, which was decorated in a deep - green tone. The ceiling lighting was a yellow silk cover which created an effect of mild daylight. The floor was covered with a deep - green carpet, and the auditorium was decorated by six ultra modern columns with elaborate up - to - date capitals. Instead of the usual restaurant Strindberg offered a lounge for the ladies and a smoking room for the gentlemen. The stage was unusually small, only 6 by 9 meters. The small stage and minimal amount of seats was meant to give the audience a greater feeling of involvement in the work. Unlike most theaters at this time, the Intima Teater was not a place in which people could come to socialize. By setting up his rules and creating an intimate atmosphere, Strindberg was able to demand the audiences focus. When the theater opened in 1907 with a performance of The Pelican it was a rather large hit. Strindberg used a minimal technique, as was his way, by only having a back drop and some sea shells on the stage for scene design and props. Strindberg was much more concerned with the actors portraying the written word than the stage looking pretty. The theater ran into a financial difficulty in February 1908 and Falck had to borrow money from Prince Eugén, Duke of Närke, who attended the première of The Pelican. The theater eventually went bankrupt in 1910, but did not close until Strindberg's death in 1912. The newspapers wrote about the theater until its death; however, Strindberg felt it was entirely unsuccessful. He felt that he never had the opportunity to successfully stage a play the way he wanted to — which was the purpose of the theater in the first place.

Strindberg died shortly after the first of his plays was staged in the United States — The Father opened on 9 April 1912 at the Berkeley Theatre in New York, in a translation by Edith and Wärner Oland.

During Christmas 1911, Strindberg became sick with pneumonia and he never recovered completely. He also started to suffer from a stomach disease, presumably cancer. He died on 14 May 1912 at the age of 63. Strindberg was interred in the Norra begravningsplatsen in Stockholm, and thousands of people followed his corpse during the funeral proceedings.

Tennessee Williams, Edward Albee, Maxim Gorky, John Osborne, and Ingmar Bergman are a few of the many people who have cited him as an influence. Eugene O'Neill, upon receiving the Nobel Prize in Literature, dedicated much of his acceptance speech to describing Strindberg's influence on his work, and referred to him as "that greatest genius of all modern dramatists."

A multi - faceted author, Strindberg was often extreme. His novel The Red Room (1879) made him famous. His early plays belong to the Naturalistic movement. His works from this time are often compared with the Norwegian playwright Henrik Ibsen. Strindberg's best - known play from this period is Miss Julie. Among his most widely read works is the novel The People of Hemsö.

Strindberg wanted to attain what he called "greater Naturalism." He disliked the expository character backgrounds that characterize the work of Henrik Ibsen and rejected the convention of a dramatic "slice of life" because he felt that the resulting plays were mundane and uninteresting. Strindberg felt that true naturalism was a psychological "battle of brains": two people who hate each other in the immediate moment and strive to drive the other to doom is the type of mental hostility that Strindberg strove to describe. He intended his plays to be impartial and objective, citing a desire to make literature akin to a science.

Following the inner turmoil that he experienced during the "Inferno crisis," he wrote an important book in French, Inferno (1896–7) in which he dramatized his experiences. He also exchanged a few cryptic letters with Friedrich Nietzsche.

Strindberg subsequently ended his association with Naturalism and began to produce works informed by Symbolism. He is considered one of the pioneers of the modern European stage and Expressionism. The Dance of Death, A Dream Play, and The Ghost Sonata are well known plays from this period.

His most famous and produced plays are Master Olof, Miss Julie, and The Father.

The history of the Paris Commune, during 1871, caused young Strindberg to develop the opinion that politics is a conflict between the upper and lower classes. He was admired by many as a far left writer. He was a socialist (or perhaps more of an anarchist, which he himself claimed on at least one occasion). Strindberg's political opinions nevertheless changed considerably within this category over the years, and he was never primarily a political writer. Nor did he often campaign for any one issue, preferring instead to scorn his enemies manifesto - style — the military, the church, the monarchy, the politicians, the stingy publishers, the incompetent reviewers, the narrow minded, the idiots — and he was not loyal to any party or ideology. Many of his works, however, had at least some politics and sometimes an abundance of it. They often displayed the conviction that life and the prevailing system was profoundly unjust and injurious to ordinary citizens.

The changing nature of his political positions shows in his changing stance on the women's rights issue. Early on, Strindberg was sympathetic to women of 19th century Sweden, calling for women's suffrage as early as 1884. However, during other periods he had wildly misogynistic opinions, calling for lawmakers to reconsider the emancipation of these "half - apes... mad... criminal, instinctively evil animals." This is controversial in contemporary assessments of Strindberg, as have his antisemitic descriptions of Jews (and, in particular, Jewish enemies of his in Swedish cultural life) in some works (e.g., Det nya riket), particularly during the early 1880s. Strindberg's antisemitic pronouncements, just like his opinions of women, have been debated, and also seem to have varied considerably. Many of these attitudes, passions and behaviors may have been developed for literary reasons and ended as soon as he had exploited them in books.

In satirizing Swedish society — in particular the upper classes, the cultural and political establishment, and his many personal and professional foes — he could be very confrontational, with scarcely concealed caricatures of political opponents. This could take the form of brutal character disparagement or mockery, and while the presentation was generally skilful, it was not necessarily subtle.

His daughter Karin Strindberg married a Russian Bolshevik of partially Swedish ancestry, Vladimir Martynovich Smirnov ("Paulsson"). Because of his political views, Strindberg was promoted strongly in socialist countries in Central and Eastern Europe, as well as in the Soviet Union and Cuba.

Strindberg, something of a polymath, was also a telegrapher, theosophist, painter, photographer and alchemist.

Painting and photography offered vehicles for his belief that chance played a crucial part in the creative process. Strindberg's paintings were unique for their time, and went beyond those of his contemporaries for their radical lack of adherence to visual reality. The 117 paintings that are acknowledged as his were mostly painted within the span of a few years, and are now seen by some as among the most original works of 19th century art. Today, his best known pieces are stormy, expressionist seascapes, selling at high prices in auction houses. Though Strindberg was friends with Edvard Munch and Paul Gauguin, and was thus familiar with modern trends, the spontaneous and subjective expressiveness of his landscapes and seascapes can be ascribed also to the fact that he painted only in periods of personal crisis. Anders Zorn also did a self portrait.

His interest in photography resulted, among other things, in a large number of arranged self portraits in various environments, which now number among the best known pictures of Strindberg.

Alchemy, occultism, Swedenborgianism, and various other eccentric interests were pursued by Strindberg with some intensity for periods of his life. In the curious autobiographical work Inferno — a paranoid and confusing tale of his years in Paris, written in French — he claims to have successfully performed alchemical experiments and cast black magic spells on his daughter.

Strindberg was married three times, as follows:

• Siri von Essen: married 1877 – 91 (14 years), 2 daughters (Karin Smirnov, Greta), 1 son (Hans); and a daughter who died in infancy
• Frida Uhl: married 1893 – 95, (2 years) 1 daughter, Kerstin, and
• Harriet Bosse: married 1901 – 02(?) (2 years), 1 daughter, Anne - Marie.

Strindberg was age 28 and Siri was 27 at the time of their marriage. He was 44 and Frida was 21 when they married and he was 52 and Harriet was 23 when they married. Late during his life he met the young actress and painter Fanny Falkner (1890 – 1963) who was 41 years younger than Strindberg. She wrote a book which illuminates his last years, but the exact nature of their relationship is debated. He had a brief affair in Berlin with Dagny Juel before his marriage to Frida; it has been suggested that the news of her murder in 1901 was the reason he cancelled his honeymoon with his third wife, Harriet. He was also related to Nils Strindberg (a son of one of August's cousins).

Strindberg's relationships with women were troubled and have often been interpreted as misogynistic by contemporaries and modern readers. Most acknowledge, however, that he had uncommon insight into the hypocrisy of his society's gender roles and sexual morality. Marriage and families were being stressed in Strindberg's lifetime as Sweden industrialized and urbanized at a rapid pace. Problems of prostitution and poverty were debated among writers, critics and politicians. His early writing often dealt with the traditional roles of the sexes imposed by society, which he criticized as unjust.

Strindberg's last home was Blå tornet in central Stockholm, where he lived from 1908 until 1912. It is now a museum.

Several statues and busts of him have been erected in Stockholm, the most prominent of which is Carl Eldh's, erected in 1942 in Tegnérlunden, a park next to the house where Strindberg lived the last years of his life.