George Santayana

(Spanish-American philosopher, 1863–1952). A celebrated figure, Santayana's first major philosophical work, The Sense of Beauty (1896), puts the view that beauty is objectified pleasure, and is considered perhaps the first book of aesthetics written in the United States. His most famous quote comes from Reason in Common Sense (1905), the first volume of his The Life of Reason: "Those who cannot remember the past, are condemned to repeat it." Santayana's major late works are Skepticism and Animal Faith (1923), and the mature articulation of his ontology, The Realms of Being (4 Vols., 1927–40), which presents an unusual and sophisticated synthesis of materialism and Platonism.

Edward Wadie Saïd

(Palestinian-American literary theorist, 1935–2003). A founding figure of post-colonial theory, Saïd is best known for his work on Orientalism, the idea that even the most outwardly objective Western texts are underwritten by a series of false assumptions about the East that serve to reinforce a Western imperialist agenda.

John Rawls

(American philosopher, 1921–2002); author of A Theory of Justice and The Law of Peoples. Rawls was an influential contributor to liberal political philosophy and his work is now engaged by a diverse range of thinkers across disciplinary boundaries, from legal theory and economics to sociology and theology.

Richard McKay Rorty

(American philosopher, 1931–2007). Rorty was one of the most important and influential philosophers writing in English during the second half of the twentieth century. He is the author of the seminal work, Philosophy and the Mirror of Nature, in which he rejects foundationalist accounts of knowledge.

W.V.O. Quine

(Influential American analytic philosopher, 1908–2000). Author of Two Dogmas of Empiricism, in which he refutes the long-standing distinction between analytic and synthetic propositions.

Hilary Whitehall Putnam

(American analytic philosopher, 1926– ). An influential thinker with original contributions to many fields including philosophy of mind, philosophy of language, philosophy of mathematics and semantics. He is best known for his hypothesis of "multiple realizability", a notion developed in the 1960s to counter the view that mental states correspond with physical states of the brain, otherwise known as the "type-identity theory". Putnam argued that it is both conceivable and probable that different organisms realize the same mental state—being in pain, for example—through radically different orientations of the central nervous system.

Alvin Carl Plantinga

(American philosopher, 1932–). Plantinga is noted for his "free will defence" to the problem of evil, his "evolutionary argument against naturalism", and the Christian religious epistemology Plantinga calls "reformed epistemology". The latter is outlined in the three-volume Warrant series; Plantinga there argues that belief in God may be rational and justified even in the absence of evidence and arguments for the existence of God.