Truthlikeness

Karl Popper introduced the formal concept in a 1960 congress address and developed it in his 1963 book Conjectures and Refutations, drawing on Alfred Tarski's correspondence theory of truth. Popper defined verisimilitude as the difference between a theory's truth content and its falsity content — a technical measure of "closeness to truth." In 1974, David Miller and Pavel Tichý independently refuted Popper's original definition, showing it could not actually rank false theories, and launched a refinement effort that continues in philosophy of science today.