From Aristotle's correspondence and Tarski's formal definition to James's pragmatism and Heidegger's unconcealment — the many theories of what 'true' means.
What makes a statement true — its match to reality, its coherence, its usefulness, or its power to unconceal?
Everyone wants the truth, but philosophers disagree sharply about what truth even is. The classical view, from Aristotle to Aquinas, defines it as correspondence: a thought or statement is true when it matches how things are. Rationalists sought a mark of truth in clear and distinct ideas; idealists tied it to the coherence of a whole system of thought; pragmatists redefined it as what proves useful and survives inquiry. The twentieth century brought both logical precision — Frege's objectivity, Tarski's formal definition — and radical suspicion, with Nietzsche and Foucault asking whose interests 'truth' serves. Heidegger reached behind the whole debate to truth as aletheia, unconcealment. Set together, these positions show that a theory of truth is never neutral: it carries a whole picture of mind, world and language.
Ancient Greek (Peripatetic)
Aristotle gives the classic formula of correspondence: 'to say of what is that it is, and of what is not that it is not, is true.' Truth and falsity lie not in things but in thought and assertion, in the combining and separating of subject and predicate. A statement is true when it says that things combined in reality are combined, or that things separated are separated.
Metaphysics, Book IV (Γ), 1011b; De Interpretatione.
Scholasticism
Truth is 'the adequation of intellect and thing' (adaequatio intellectus et rei) — the conformity of mind to reality. Yet things are themselves true in relation to the divine intellect that thinks them, so created things are measured by God's mind and measure our minds in turn. Truth resides primarily in the judging intellect, and God, as the first truth, is truth itself.
Disputed Questions on Truth (De Veritate), q. 1; Summa Theologiae, I, q. 16.
Rationalism
Seeking an indubitable foundation, Descartes finds it in the cogito and then adopts a criterion of truth: whatever I perceive very clearly and distinctly is true. The reliability of this criterion is secured by a non-deceiving God, who would not let my clearest perceptions systematically mislead me. Error arises when the will affirms beyond what the understanding clearly grasps.
Meditations on First Philosophy (1641), III–IV.
Critical philosophy
Kant accepts the nominal definition of truth as agreement of knowledge with its object, but denies we can have a universal material criterion of it. His 'Copernican turn' holds that objects must conform to the forms of our intuition and the categories of understanding, so truth concerns appearances structured by the mind, not things-in-themselves. Logical truth is mere non-contradiction; empirical truth requires that intuitions be brought under concepts within possible experience.
Critique of Pure Reason (1781/1787), 'Transcendental Logic'.
German idealism
For Hegel truth is not the correctness of an isolated proposition but 'the whole' — the systematic self-development of the Concept in which subject and object are ultimately united. A thing is 'true' when it accords with its own concept, and philosophical truth unfolds dialectically, so that partial standpoints are preserved and superseded (aufgehoben) in a fuller totality. 'The True is the whole,' realized only through its own becoming.
Phenomenology of Spirit (1807), Preface; Science of Logic.
Existentialism (proto-)
Against Hegel's objective system, Kierkegaard insists that for the existing individual 'truth is subjectivity' — what matters is the how of one's inward, passionate appropriation, not merely the what of an objective proposition. Regarding the highest matters, especially faith, 'an objective uncertainty held fast in an appropriation-process of the most passionate inwardness is the truth.' Truth is something to be lived, not just known.
Concluding Unscientific Postscript (1846).
Genealogical critique
Nietzsche unmasks the 'will to truth' and asks what it costs and whom it serves. Truths are 'a mobile army of metaphors' that we have forgotten are metaphors, useful fictions congealed by habit into supposed facts. His perspectivism holds that there are no facts, only interpretations, and that our valuing of truth over life-serving illusion is itself a value to be questioned.
'On Truth and Lie in a Nonmoral Sense' (1873); On the Genealogy of Morals (1887).
Pragmatism
Peirce defines truth as the ideal end of inquiry: 'the opinion which is fated to be ultimately agreed to by all who investigate is what we mean by the truth.' Truth is what a community of inquirers would converge on if investigation were carried far enough, and reality is the object represented in that final opinion. Belief is fixed reliably only by the self-correcting method of science.
'How to Make Our Ideas Clear' (1878); 'The Fixation of Belief' (1877).
Pragmatism
James makes truth a species of the good: 'the true is only the expedient in the way of our thinking.' An idea becomes true insofar as it works — helps us deal with experience, links parts of it satisfactorily, and 'pays' in the long run. Truth is not a static relation of copying but something that 'happens to an idea' through its verification and practical fruits.
Pragmatism (1907), Lecture VI, 'Pragmatism's Conception of Truth'.
Analytic philosophy / logic
Frege argues that truth is indefinable and primitive: any attempt to define it as correspondence covertly presupposes it, since we would have to ask whether it is true that the correspondence holds. Truth is objective and mind-independent — the laws of logic are the 'laws of truth,' not descriptions of how we happen to think. The truth-value of a sentence is what its sense (a thought) determines, and thoughts belong to a 'third realm' beyond the psychological.
'The Thought' (Der Gedanke, 1918); The Foundations of Arithmetic (1884).
Logic / semantics
Tarski gives a rigorous semantic definition of truth for formalized languages, capturing the intuition of the schema: '‘Snow is white’ is true if and only if snow is white.' His 'Convention T' requires that an adequate definition entail every such equivalence, defining truth recursively via satisfaction. He also shows that truth for a language cannot be consistently defined within that same language, requiring a richer metalanguage.
'The Concept of Truth in Formalized Languages' (1933); 'The Semantic Conception of Truth' (1944).
Phenomenology / hermeneutics
Heidegger argues that correspondence is derivative from a more original truth: aletheia, 'unconcealment.' Before any statement can match a fact, entities must first be disclosed, brought out of hiddenness into the open, which happens through the being of Dasein and its world. Truth is thus an event of revealing that always carries concealment with it; the propositional 'correctness' of the tradition rests on this deeper happening.
Being and Time (1927), §44; 'On the Essence of Truth' (1930).
Post-structuralism
Foucault studies not truth in the abstract but the historically shifting 'regimes of truth' — the systems of power and discourse that decide which statements can count as true or false. 'Truth is a thing of this world,' produced by institutions, procedures and disciplines, and it is bound up with power in a circular relation. The task is not to liberate truth from power but to detach the power of truth from the specific forms of hegemony under which it operates.
'Truth and Power' (1977); Discipline and Punish (1975).