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John Searle John Rogers Searle, born in Denver (Colorado) in 1932 and died in 2025, was Professor Emeritus at the University of California, Berkeley. His contributions span philosophy of language (speech act theory), philosophy of mind (the Chinese Room argument, biological naturalism), and social ontology (the construction of institutional reality). He is one of the most widely read and debated analytic philosophers of the 20th and early 21st centuries. Key Concepts Speech Act Theory (Speech Acts, 1969): Developing J.L. Austin, Searle systematises the theory. Every speech act involves: ...

John Stuart Mill Born in London in 1806, John Stuart Mill was subjected by his father, James Mill, to an extraordinarily precocious and rigorous education — designed by Bentham’s circle to form a utilitarian thinker: he learned Greek at the age of three and devoured the classics and economics in childhood. At twenty he suffered a profound existential crisis, from which he recovered partly through Romantic poetry — an experience that led him to correct the arid utilitarianism in which he had been raised. He was also an economist, a Member of Parliament, and the intellectual companion of Harriet Taylor. He became the most influential liberal of the nineteenth century. ...

Born in Moquegua, Peru, in 1894, José Carlos Mariátegui overcame a poor childhood and fragile health — which would cost him a leg and later confine him to bed — to become, as a self-taught thinker, the most original Marxist of Latin America. A combative journalist, he spent some years in Italy, where he absorbed Marxism and the ideas of Croce and Sorel; back in Peru, he founded the influential journal Amauta and the Socialist Party. He died in 1930, at only 35, leaving a brief and dazzling body of work. ...

Joseph Maréchal was a Belgian Jesuit philosopher and psychologist, founder of Transcendental Thomism — a movement that undertook a synthesis between Thomistic metaphysics and Kant’s critical philosophy. His work marks a decisive moment in the renewal of Scholasticism in the 20th century and exerted profound influence on figures such as Karl Rahner and Bernard Lonergan. Key Concepts The Starting Point of Metaphysics (Le Point de départ de la Métaphysique, 5 notebooks, 1922–1947): His principal work. Maréchal traces the history of epistemology — from Greek philosophy through Kantianism — to ground Thomistic metaphysics in the face of Kantian critique. Notebook V (“Thomism Confronting Critical Philosophy”) is the most discussed. ...

Joshua Greene Joshua Greene (b. 1974) is a professor of psychology and director of the Moral Cognition Laboratory at Harvard University. His work stands at the intersection of moral philosophy, experimental psychology, and cognitive neuroscience, and it represents one of the most prominent efforts in the empirical turn within contemporary ethics. Greene does not merely describe how people reason about moral questions; he uses that data to defend an explicit normative claim — that utilitarianism, or more precisely what he calls “deep pragmatic utilitarianism,” is the most defensible theory for adjudicating conflicts among groups with incompatible value systems. ...

Judith Butler American philosopher; central figure in queer theory and gender studies. Gender Trouble (1990) transformed the humanities by proposing that gender is not a fixed identity, but a performance. Born in Cleveland, Ohio, in 1956, Butler completed her doctorate in philosophy at Yale University in 1984 with a dissertation on the French reception of Hegel. Her intellectual formation draws on French existentialism, phenomenology, and post-structuralism — a combination that enabled her to interrogate categories typically treated as natural, such as “sex,” “gender,” and “subject,” in terms of their historical production. The central problem driving her work is: how do cultural norms fabricate bodies and identities that pass as natural? This question places her at the intersection of continental philosophy, feminist theory, and minority politics. ...

Judith Jarvis Thomson Judith Jarvis Thomson (1929–2020) was a professor at the Massachusetts Institute of Technology (MIT) and one of the most rigorous voices in American analytic ethics during the second half of the twentieth century. Her work is distinguished by its meticulous analysis of concrete cases and its systematic use of thought experiments as testing devices for general moral principles. Educated at Columbia University and at Cambridge (UK), she devoted decades to the examination of rights, moral permissibility, causation, and responsibility — with particular attention to situations in which strong intuitions collide with otherwise coherent normative theories. ...

Julia Kristeva Julia Kristeva (born 24 June 1941 in Sliven, Bulgaria) is a Bulgarian-French philosopher, psychoanalyst, linguist, semiotician, and novelist. She arrived in Paris in 1965 on a doctoral fellowship and soon joined the group around the journal Tel Quel, the epicenter of the French intellectual avant-garde. She became a professor at the University of Paris VII and a practicing psychoanalyst. Her work cuts across linguistics, literary theory, psychoanalysis, and philosophy, with a strong debt to Bakhtin, Saussure, and Lacan. ...

Jürgen Habermas Born in 1929 in Germany, and marked in his youth by the experience of Nazism and the postwar period, Jürgen Habermas became the leading name of the second generation of the Frankfurt School and one of the most influential philosophers of recent decades (he died in 2026). An assistant to Adorno, he inherited the tradition of Critical Theory but rejected its pessimism: where Horkheimer and Adorno saw modern reason degenerate into sheer domination, Habermas sought to recover an emancipatory potential within reason itself. ...

Karl Jaspers German psychiatrist and philosopher, one of the central figures of the philosophy of existence alongside Heidegger and Kierkegaard. He moved from psychiatry (General Psychopathology, 1913) to philosophy, developing a reflection on human existence centered on boundary situations, existential communication, and transcendence. He was Hannah Arendt’s mentor at Heidelberg. After World War II, he became an influential voice on the question of German guilt and the ethical foundations of politics. ...

Karl Marx Born in Trier, in the Prussian Rhineland, in 1818, Karl Marx studied law and philosophy in Bonn and Berlin, where he drew close to the Young Hegelians. Barred from an academic career by his radical positions, he turned to journalism and, hounded by censorship, went into exile in Paris, Brussels, and finally London, where he lived through decades of poverty, sustained by his friend and collaborator Friedrich Engels and poring over the economists in the Reading Room of the British Museum. More than to interpret the world, he wanted to transform it: “the philosophers have only interpreted the world in various ways; the point, however, is to change it” (Thesis 11 on Feuerbach). ...

Karl Popper Austrian-British philosopher. Proposed falsificationism as a criterion for scientific demarcation and defended the open society against totalitarianism. Sharp critic of Marxism and historicism. Born in Vienna in 1902, Popper came of age in intellectual contact with the Vienna Circle — the group of philosophers and scientists who sought to ground knowledge in strict verificationist terms. Rather than joining their programme, however, he turned the question around: the central problem of epistemology is not how we confirm theories, but how we distinguish genuine science from pseudo-science. His answer, falsificationism, holds that the hallmark of a scientific theory is its refutability: a claim is scientific if and only if it is possible to conceive of an observation or experiment that could prove it wrong. This methodological reorientation, set out in The Logic of Scientific Discovery (1934), reshaped the foundations of twentieth-century philosophy of science. ...

Kimberlé Crenshaw Kimberlé Williams Crenshaw (born 1959 in Canton, Ohio) is an American legal scholar and professor of law at UCLA and Columbia University. She is one of the founders of Critical Race Theory and the author who coined the concept of intersectionality, now central to gender studies, race studies, and political philosophy, but originally formulated within antidiscrimination law. The problem she starts from is practical and legal. Analyzing discrimination cases — especially DeGraffenreid v. General Motors (1976), in which Black women were left legally unprotected because the company hired (white) women and (male) Black workers — Crenshaw showed that single-axis frameworks (discrimination either by race or by gender) rendered invisible the situation of those who stand at the intersection of more than one axis. ...

Kurt Godel Kurt Gödel is widely regarded as the greatest logician since Aristotle. Born in Brünn (now Brno, Czech Republic) on 28 April 1906, and died in Princeton on 14 January 1978, his work fundamentally transformed mathematical logic, the foundations of mathematics, and the philosophy of mind. His two Incompleteness Theorems (1931) partially dismantled David Hilbert’s formalist programme and established intrinsic limits to any sufficiently powerful axiomatic system. Key Concepts First Incompleteness Theorem (Über formal unentscheidbare Sätze der Principia Mathematica und verwandter Systeme I, 1931): Gödel proved that any consistent formal system capable of expressing elementary arithmetic necessarily contains propositions that can neither be proved nor refuted within the system itself. The proof strategy is remarkably ingenious: Gödel encoded formal syntax by means of numbers (the so-called Gödel numbering), thereby constructing a sentence that, in its own arithmetic numbering, asserts “I am not provable in this system.” If the system could prove this sentence, it would be inconsistent; since it cannot, the sentence is true yet undecidable. The theorem showed that completeness — the capacity of a formal system to decide every well-formed proposition — is incompatible with consistency, for sufficiently expressive systems. ...

Kwame Anthony Appiah Kwame Anthony Appiah was born on 8 May 1954 in London, to a Ghanaian father (Joe Appiah, lawyer and politician) and a British mother (Peggy Cripps). He grew up in Kumasi, Ghana, and studied philosophy at Cambridge (BA and PhD). He has taught at Yale, Cornell, Duke, Harvard, and Princeton; he is currently professor at New York University. Appiah is one of the most versatile and influential philosophers in the contemporary anglophone world, with contributions to ethics, philosophy of language, philosophy of mind, racial theory, and political philosophy. He is one of the thinkers who has most systematically challenged the presuppositions of “racialism” — the belief that human races exist as biological entities endowed with moral and intellectual essences. ...

Kwame Nkrumah Kwame Nkrumah (21 September 1909 – 27 April 1972) was born in Nkroful, Gold Coast (present-day Ghana). He studied in the USA (Lincoln University and University of Pennsylvania) and the United Kingdom (London School of Economics), where he developed his Pan-Africanist ideas in contact with figures such as C.L.R. James and George Padmore. He returned to the Gold Coast in 1947, led the independence movement, and became the first president of Ghana in 1957 — the first sub-Saharan African country to gain independence in the postwar period. He was deposed in a military coup in 1966 while in Beijing, en route to Hanoi. He spent the rest of his life in exile in Guinea-Conakry, where he died in 1972. Nkrumah is regarded as one of the founding fathers of modern Pan-Africanism and a central figure of the Organisation of African Unity (founded 1963). ...

Laozi (老子) Essential historical note: The existence of Laozi as an individual historical figure is debated among specialists. The historian Sima Qian (c. 145–86 BCE), in the Shiji, records several traditions about Laozi without being able to decide between them — an indication that the uncertainty is ancient. The text attributed to him, the Dàodéjīng (道德經, “Classic of the Way and Virtue”, also called the Laozi), may be a compilation of material from different sources; modern scholarship places the current form of the text in the 4th or 3rd century BCE. The figure of Laozi as an ancient sage who supposedly met Confucius and then left China westward is probably legendary. ...

Léopold Sédar Senghor Léopold Sédar Senghor (9 October 1906, Joal, Senegal — 20 December 2001, Verson, France) was a poet, philosopher of culture, and statesman. The first president of independent Senegal (1960–1980) and the first African elected to the Académie française (1983), he was also, alongside Aimé Césaire and Léon-Gontran Damas, one of the founders of Négritude in 1930s Paris. While Césaire gave the movement its poetic force, Senghor set out to give it a systematic philosophical and aesthetic elaboration, making of it a general theory of the African contribution to human civilization. His work is today the object of both recognition and lively controversy. ...

Leopoldo Zea Born in Mexico City in 1912, Leopoldo Zea was a disciple of José Gaos — the exiled Spanish philosopher who brought the legacy of Ortega y Gasset to Mexico. Zea became the foremost historian of Latin American philosophy and the central figure in a decisive debate: is there a properly Latin American philosophy, or does the region merely repeat European thought? His answer is affirmative and liberating. Inheriting from Ortega the idea that we always think from a circumstance (“I am myself and my circumstance”), Zea argues that the American philosopher must depart from his or her own concrete historical situation — without an inferiority complex and without awaiting European validation. Hence his motto: Latin American philosophy is “philosophy, nothing more” (filosofía sin más), as legitimate as any other, with no need for adjectives that would relegate it to a lesser status. ...

Lewis Mumford Lewis Mumford was born in Flushing, Queens, New York, on 19 October 1895, and died in Amenia, New York, on 26 January 1990. He studied at the City College of New York and at the New School for Social Research but never completed a formal degree — tuberculosis contracted in his youth interrupted his studies, and he later served as a radio electrician in the United States Navy during the First World War. A largely self-taught polymath, Mumford produced one of the twentieth century’s most influential bodies of work on the history of technics, the city, and architecture, while also serving as associate editor of The Dial and, for more than three decades, as architecture critic for The New Yorker. His intellectual formation owed more to Patrick Geddes — the Scottish urbanist and biologist whom Mumford called his “avowed master” — than to any academic institution; from Geddes he inherited a periodization of the phases of technics and a holistic approach integrating biology, sociology, and technology. He also absorbed from Thorstein Veblen a critique of absentee ownership and wasteful production, and from Peter Kropotkin and Ebenezer Howard the ideal of a cooperative, regionalist urbanism. ...