110 thinkers, books, and ideas connected to this field.
Mill's A System of Logic (1843) is the foundational work of empiricist logic and philosophy of science, defending inductive reasoning as the basis of all knowledge.
British philosopher of mathematics who has worked on logicism, the nature of mathematical knowledge, and the philosophy of mathematics.
German-Israeli mathematician who developed nonstandard analysis — making rigorous the use of infinitesimals in calculus through model theory — rehabilitating the intuitive approach of Leibniz and Newton.
The view in philosophy of mathematics that abstract objects (numbers, sets) are obtained by abstracting from concrete instances — identifying equivalence classes under abstraction principles like Hume's Principle.
The dominant tradition in British and American academic philosophy since the early 20th century, characterized by rigorous argumentation, formal logic, conceptual analysis, and engagement with science and language.
Dutch logician who was the leading expert on intuitionistic logic and constructive mathematics — writing the definitive metamathematical studies of intuitionistic systems.
Italian-born Archbishop of Canterbury who developed the ontological argument for God's existence and a satisfaction theory of atonement, pursuing faith seeking understanding (fides quaerens intellectum).
French theologian, philosopher, and logician who was the leading Jansenist controversialist and co-authored the Port-Royal Logic — one of the most influential logic textbooks of the 17th century.
Ghanaian philosopher who was brought to Europe as a child, earned a doctorate at Halle, and produced original philosophical work on the nature of the human mind and sensation.
Ancient Greek philosopher — student of Plato — founder of the Lyceum — who created formal logic, founded comparative biology, wrote foundational texts in ethics (Nicomachean Ethics), politics, rhetoric, poetics, and physics — whose works dominated Western thought for 2000 years.
New Zealand logician who founded tense logic — modal logic for time — and contributed to the philosophy of time and ethics.
The opening dialectic of Hegel's Science of Logic — Being and Nothing are identical in their indeterminacy; their unity and difference generates Becoming — the first movement of speculative logic.
Loosely organized Berlin group of philosophers and scientists associated with logical empiricism, centered on Hans Reichenbach and the journal Erkenntnis.
Czech mathematician, logician, and philosopher who anticipated Frege and Husserl by positing abstract propositions and ideas in themselves (Sätze an sich), independent of any mind.
British philosopher and mathematician — author of Principia Mathematica (with Whitehead), The Problems of Philosophy, and A History of Western Philosophy — Nobel Prize in Literature (1950) — who founded analytic philosophy, created Russell's Paradox, and was a prominent peace activist.
Indian philosopher at Oxford who was the most important figure in making classical Indian philosophy (Nyaya, Mimamsa, Vedanta) available to analytic philosophers — demonstrating that Indian philosophical traditions engage the same problems as Western philosophy with equal rigor.
Late Roman philosopher, statesman, and theologian who transmitted Greek philosophy to the Latin Middle Ages through his translations of Aristotle and the Consolation of Philosophy, written while awaiting execution.
American philosopher who has contributed to the Internet Encyclopedia of Philosophy and written on the philosophy of time and informal logic.
The Brouwer-Heyting-Kolmogorov (BHK) interpretation of intuitionistic logic — a proposition is true if and only if there is a proof of it; the meaning of each logical connective is defined in terms of what counts as a proof.
American pragmatist philosopher who invented modern modal logic (as an alternative to Russell-Whitehead's extensional logic) and developed a pragmatist epistemology based on the given in experience and conceptual schemes.
American philosopher who co-authored a widely used logic textbook with Copi and wrote against affirmative action from a liberal perspective.
German-American philosopher of science who developed the deductive-nomological (covering-law) model of scientific explanation and posed the raven paradox for the confirmation theory of science.
Aristotle's classification of the ten basic ways in which things can be said to be — substance, quantity, quality, relation, place, time, position, state, action, passion.
Greek philosopher who became the third head of the Stoic school and systematized its logic, physics, and ethics into a comprehensive philosophical system.
A fundamental theorem of first-order logic: a set of sentences has a model if and only if every finite subset of it has a model.
The mathematical program requiring that proofs of existence be constructive — providing a method to exhibit or compute the object, rather than merely demonstrating that its non-existence leads to contradiction.
American philosopher at University of Texas who has worked on logic, deontic logic, and conditional norms, and is known for widely used logic textbooks.
American philosopher who developed the formal semantics of indexicals and demonstratives, distinguishing character from content.
American philosopher who defended modal realism — the view that possible worlds are concrete, spatiotemporally isolated universes — and made foundational contributions to semantics, mind, and metaphysics.
The axioms characterizing the natural numbers — zero is a natural number, every natural number has a successor, zero is not the successor of any number, different numbers have different successors, and induction — providing the standard foundation for arithmetic.
David Kaplan's foundational essay developing the formal logic of indexicals and demonstratives, distinguishing character from content.
Dutch logician and philosopher of mathematics who wrote the definitive biography of Brouwer and co-authored the reference work on constructive mathematics.
Israeli-British logician who has contributed to modal logic, temporal logic, labelled deductive systems, and is the editor of the most comprehensive reference work in philosophical logic.
A logical framework combining epistemic logic with dynamic logic to model how agents' knowledge and beliefs change in response to communication, observation, and action.
Swedish logician who worked on dependent type theory, formal topology, and constructive foundations of mathematics.
German philosopher who has worked on formal logic, philosophy of language, and the foundations of ethics, contributing to German analytic philosophy.
American logician and philosopher of mathematics who developed plural quantification, rehabilitated Frege's logicism via neo-logicism, and wrote on provability logic.
A placeholder person used in philosophical thought experiments concerning 2D semantics alongside Anand.
Finnish philosopher who founded modern deontic logic (the logic of obligation and permission), developed an action-theoretic approach to causation and explanation, and served as Wittgenstein's literary executor.
Italian logician who developed formal topology — a point-free, constructive account of topology — and the Basic Picture, a framework for constructive foundations.
German philosopher and mathematician who invented calculus independently, developed monadology — the view that reality consists of simple, immaterial, windowless monads — and argued this is the best of all possible worlds.
German polymath who co-invented calculus independently of Newton, developed the theory of monads, proposed possible worlds semantics, and attempted a universal symbolic logic.
German mathematician and philosopher who invented modern predicate logic and introduced the sense/reference distinction, founding analytic philosophy of language.
German philosopher of science who developed a frequency theory of probability, a pragmatic vindication of induction, and the philosophical analysis of relativity theory.
German logician who has worked on proof theory and the extraction of programs from constructive proofs — the formal realization of the Curry-Howard correspondence.
Australian philosopher who has made extensive contributions to the philosophy of language and modal logic, particularly concerning the analysis of connectives and the logic of indexicals.
American logician who wrote Introduction to Logic — the most widely used introductory logic textbook in the 20th century, in print for over 60 years.
English Nonconformist minister, hymnwriter (When I Survey the Wondrous Cross), and author of Logick (1725) — one of the most widely used logic textbooks in 18th century England and America.
American philosopher — Provost of Stanford (2000–2017) — co-founder of Stanford's Human-Centered AI Institute (HAI) with Fei-Fei Li — logician who has been at the center of Stanford's AI governance efforts.
American logician and philosopher who extended the stit theory of agency to deontic logic, developing a formal theory of obligation based on agency in branching time, and contributed to the logic of defaults and reasons.
Austrian-American logician and mathematician — author of the Incompleteness Theorems (1931) — who proved that any consistent formal system capable of expressing arithmetic contains true statements that cannot be proved within the system — the most significant result in the foundations of mathematics.
Austrian-American logician who proved the incompleteness theorems — any consistent formal system strong enough to express arithmetic contains true statements it cannot prove — transforming logic, philosophy of mathematics, and epistemology.
American philosopher who has worked on the logic of indexical expressions and theories of reference.
Belgian philosopher who worked on logic, philosophy of science, and the theory of worldviews — arguing that everyone operates with an implicit worldview that philosophy should make explicit.
American logician who provided a simplified and generalized proof of Gödel's completeness theorem using the Henkin construction — adding witness constants to extend consistent theories to complete consistent theories.
Same entity as Leon A. Henkin (ID 252) — American logician who proved completeness of first-order logic via the Henkin construction.
The Port-Royal Logic (La Logique ou l'Art de Penser) by Antoine Arnauld and Pierre Nicole — the most widely used logic textbook in Europe for over a century, combining traditional syllogistic with probability reasoning.
Austrian-British philosopher — author of the Tractatus Logico-Philosophicus and Philosophical Investigations — who created two completely different philosophies (early: logic as the limit of language; late: language as family resemblance in forms of life) — the most influential philosopher of the 20th century in the analytic tradition.
New Zealand mathematician working on constructive mathematics and paraconsistent logic.
British-American analytic philosopher who contributed to the philosophy of language, logic, and metaphysics — famous for the thought experiment against Leibniz's principle of the identity of indiscernibles.
Avicenna's Kitab al-Shifa (Book of the Remedy/Healing) — the most comprehensive philosophical encyclopedia of the medieval world, covering logic, natural science, mathematics, and metaphysics in the Aristotelian tradition.
British philosopher who developed anti-realism — the meaning of a statement is given by its assertibility conditions, not its truth conditions — and produced the authoritative scholarly interpretation of Frege.
American logician who collaborated with Nuel Belnap and Ming Xu on developing the stit (sees to it that) theory of agency and action.
Chinese-American logician who contributed to the development of the stit (sees to it that) theory of agency and branching-time logic.
Ancient Chinese philosopher and founder of Mohism, who argued for universal, impartial love (jian ai) as the solution to social disorder, opposing Confucian role-based ethics with a proto-utilitarian framework.
Steven Landsburg's 2007 collection of economic arguments leading to counterintuitive conclusions — including the title thesis (that more sexually active people expanding the pool of cautious partners reduces HIV transmission).
Chinese philosopher who founded Mohism — opposing Confucianism — with the doctrine of jian ai (universal, impartial love), consequentialist ethics, and active opposition to aggressive warfare.
American philosopher and one of the most prolific philosophers in history — over 100 books — who developed a pragmatic idealism arguing that knowledge is a practical achievement of mind in interaction with a mind-independent world.
American logician who developed branching-time logic, the stit (sees to it that) theory of action, and four-valued logic for reasoning with incomplete or inconsistent information.
Aristotle's treatise on propositions, truth, and falsity — including the famous sea battle argument about future contingents.
Italian-American philosopher of mathematics who has worked on mathematical explanation, abstraction principles in neo-logicism, and the history of 20th century logic.
Ancient Greek philosopher from Elea who argued in verse that only being exists, non-being is inconceivable, and all apparent change and multiplicity is illusion — founding Western metaphysics' preoccupation with the one and the many.
French philosopher and theologian — who created conceptualism (the middle way between realism and nominalism) — whose affair with Héloïse and subsequent castration is the most famous personal catastrophe in medieval intellectual history — whose Sic et Non established the scholastic method.
British analytic philosopher who made foundational contributions to the logic of predicates and ethical theory, including the Geach-Frege point about the embedding of moral terms in unasserted contexts.
Swedish philosopher who has worked on compositionality of meaning, the nature of assertion, and communicative content.
Jansenist theologian and moralist who co-authored the Port-Royal Logic with Antoine Arnauld and analyzed the role of self-love (amour-propre) in social morality.
Aristotle's account of scientific knowledge as demonstration from first principles through syllogisms, distinguishing demonstrative knowledge from mere opinion.
Three-volume collaborative work by Bertrand Russell and Alfred North Whitehead attempting to derive all of mathematics from purely logical axioms using type theory.
Aristotle's systematic treatment of syllogistic logic — the first formal system in the history of logic — classifying all valid syllogistic forms.
American philosopher who has made major contributions to neo-logicism (proving and analyzing Frege's Theorem) and to the philosophy of language.
American logician who contributed to formal pragmatics, worked with Richard Montague on intensional logic, and has worked on logics of belief.
American philosopher who wrote influential studies of Wittgenstein and Hume and contributed to informal logic pedagogy.
American philosopher who developed a possible worlds semantics for conditionals and a pragmatic theory of assertion based on common ground.
Dutch-Australian computer scientist who has worked on the logic of knowledge and deontic logic in the context of artificial intelligence and security.
American philosopher of mathematics who has worked on neo-logicism, the paradoxes of self-reference, and the logic of comics.
German-American philosopher and central figure of the Vienna Circle who developed logical empiricism, the linguistic framework theory of metaphysics, and intensional semantics.
Descartes's early unpublished work (Regulae ad Directionem Ingenii) outlining rules for the proper direction of the mind toward certain knowledge — the methodological foundation for his later Meditations.
American philosopher and logician who revolutionized philosophy of language through modal logic semantics, the causal theory of names, and the distinction between necessity and apriority.
Abelard's compilation of 158 theological questions with contradictory answers from Church authorities, without providing resolutions — demonstrating the necessity of rational dialectic in theology.
Plato's late dialogue in which the Eleatic Stranger attempts to define the sophist — leading to a radical revision of Parmenidean metaphysics and an account of how false statements are possible.
American philosopher of mathematics who developed ante rem structuralism — mathematical objects are positions in structures that exist independently of their instantiations — and has written on philosophy of logic.
Hellenistic philosophical school founded by Zeno of Citium holding that virtue alone constitutes eudaimonia, that the universe is rational and providentially ordered, and that emotions contrary to reason are errors of judgment.
Canadian philosopher who developed a branching-universe model of objective becoming — the actual future is selected by a process of branch attrition as possibilities are eliminated.
Ockham's comprehensive treatise on logic — the most systematic presentation of medieval nominalist logic, covering terms, propositions, and syllogistics.
Kit Fine's systematic investigation of neo-Fregean abstractionism, examining which abstraction principles are acceptable and what the limits of the neo-logicist program are.
Rudolf Carnap's attempt to rationally reconstruct all empirical knowledge starting from phenomenal primitives using logical construction, demonstrating the systematic unity of science.
British philosopher who developed the knowledge-first epistemology — knowledge is the most fundamental epistemic state, not analyzable into justified true belief — and has contributed to the logic of vagueness and modal epistemology.
Aristotle's treatise on dialectical reasoning — the art of arguing from generally accepted opinions (endoxa) to conclusions — providing a handbook for philosophical debate.
Ludwig Wittgenstein's early systematic work arguing that language pictures the logical structure of facts, and that what cannot be said — ethics, aesthetics, the mystical — must be passed over in silence.
Canadian philosopher who contributed to the development of informal logic as a discipline and has written on forgiveness, social trust, and reconciliation.
Viennese philosophical discussion group (1924-1936) led by Moritz Schlick that developed logical empiricism — the application of mathematical logic to scientific philosophy and the verificationist criterion of meaning.
American philosopher who dismantled the analytic-synthetic distinction and meaning-theoretic foundationalism in Two Dogmas of Empiricism, developed naturalistic epistemology, and argued for an inscrutability of reference.
American philosopher who rejected the analytic/synthetic distinction and defended a thoroughgoing naturalized epistemology — making him the most influential American philosopher of the 20th century.
French medieval philosopher and theologian who defended extreme realism about universals and was famously refuted by his student Abelard.
English Franciscan friar and philosopher who developed nominalism — the view that universals are merely names, not real entities — and is associated with the parsimony principle known as Ockham's Razor.
Cypriot-Greek philosopher who founded Stoicism after studying in Athens, teaching in the Stoa Poikile — the Painted Porch — from which the school takes its name.
The standard axiomatic foundation for mathematics — a list of axioms about sets (extensionality, pairing, union, power set, infinity, replacement, foundation) that avoid the Russell and Burali-Forti paradoxes and suffice to develop virtually all mathematics.
Norwegian philosopher who has contributed to plural logic, neo-logicism, and a potentialist interpretation of set theory — sets are not fully formed objects but potential collections.
Frege's 1892 essay introducing the distinction between Sinn (sense/mode of presentation) and Bedeutung (reference/denotation), resolving the puzzle of informative identity statements.