Rainer Maria Rilke was a poet universally described as "mystical," and always attracted a large following from the time he first published in the 1890s. Franz Xaver Kappus, a nineteen-year-old cadet at the Theresian Military Academy, received ten letters on poetry from Rilke from 1902 to 1908. In 1928, three years after Rilke died of leukemia, Kappus collected and published the letters as Letters to a Young Poet.

In Cold Blood was considered the first "non-fiction novel" shortly after the book's publication. Its author, Truman Capote, was already an acclaimed author, and sought out the story of two murderers, Richard Hickock and Perry Smith. Capote interviewed and talked with the murderers for over a year to craft his book, which became a bestseller as soon as it was published.

It was Edmund Husserl who inaugurated the movement known as Phenomenology. He was closely concerned with issues pertaining to the foundations of mathematics and logic as well as numerous questions in psychology being discussed in his time. Phenomenology became a wide and varied field, incorporating many thinkers throughout the 20th century. It remains a major school of thought, though its influence has become more diffuse. Husserl believed that he was providing a form of philosophy that overcame the modern problem of Idealism, allowing philosophers once again to discuss the "things in themselves." Phenomenology became a study of the way that things "appear"—how they come into awareness and just how they are constituted by the human knower. He is known for works such as Logical Investigations, Ideas (in numerous versions), Cartesian Meditations, and Formal and Transcendental Logic.

Educated as psychiatrist, Frantz Fanon was born in Martinique and lived for a long time in Algeria, where he fought in the Algerian revolution against France. As a black man fighting against European powers, Fanon developed many theories about the psychological effect of colonialism. His final work, The Wretched of the Earth, made as he was dying of leukemia in 1961, argued that a colonial people had the right to fight their rulers and demand their freedom, and became highly influential for a variety of left wing revolutionaries in the late twentieth century.

Perhaps you do not know all of these thinkers, though the names are likely to be somewhat known to you, at least from lists in texts. Sadly, America has not existed long enough to create a large group of philosophers as was the case in ancient Greece, the High Middle Ages (or even the so-called period of "Silver Scholasticism" in Spain and the Low Countries), or modern Europe. Still, there have been some, but among their number has never been Bertrand Russell. Lord Russell is an Englishman—a great logician and mathematician but not an American philosopher.

After the heterodox Christian Søren Kierkegaard in the nineteenth century, the philosophical movement known as existentialism was largely picked up by atheists. However, in the post-World War II period, the Christian theologian Paul Tillich embraced many of existentialism's chief tenets, including alienation, an inability to know things concretely, and the desire for an authentic life. This made Tillich simultaneously controversial and widely celebrated.

The 20th century political philosopher, Leo Strauss, believed that many political and philosophical writings contain esoteric meanings. He came to this conclusion based on his interpretations of the writings of the Muslim philosopher al-Farabi and the dialogues of Plato. Plato's dialogues are particularly well known for the use of many layers of irony, wit, and story to express deep philosophical truths. Strauss (and his followers, who are called "Straussians") came to use this method for interpreting many texts.

He was very influential, given his time as a professor at the University of Chicago, and is often associated with the American political movement known as neoconservatism. This association is not quite true, however. Really, if his followers share anything in common, it is a devotion to a close reading of texts, often those of Greek thinkers but also including others in the canon of philosophy and political philosophy. Their readings do tend to be so close as to look for many such hidden shades of esoteric meanings.

Ludwig Wittgenstein's considerable fame as a philosopher comes on the strength of just two books. Tractatus Logico-Philosophicus was a slim book published in 1921, while Wittgenstein's Philosophical Investigations were compiled after his death from his notebooks and published in 1953. The Philosophical Investigations were largely a refutation and rebuttal of Wittgenstein's earlier work.

Existentialism was a disparate philosophical movement that emerged in the nineteenth century through the writings of Soren Kierkegaard, Friedrich Nietzsche, and Fyodor Dostoyevsky. Largely focusing on the individual and the subjectivity of human thought, existentialism was a critical reaction to philosophers such as Immanuel Kant and Georg Wilhelm Friedrich Hegel. Existentialism would further develop in France during the first half of the twentieth century thanks to figures like Jean-Paul Sartre, Simone de Beauvoir, and Albert Camus.

The Myth of Sisyphus, written by Albert Camus during the Nazi Occupation of France in World War II, uses the ancient story of Sisyphus to explain life. Just as Sisyphus was doomed to continually push a rock up a hill, Camus argued people had a life with little meaning. Nonetheless, he argued that humans should strive to rebel against the absurdity of such a life.