falsity

Falsity is the property of being false or untrue. In ordinary use, a proposition, claim, belief, or statement is said to be false if it does not correspond to reality or to what is the case. In philosophy and logic, falsity is often contrasted with truth as the status of a statement within a given framework or model.

The term derives from Latin falsitas, from falsus “false,” via Old French falsité. The word has long been used in logic, epistemology, and rhetoric to denote that a claim fails to meet a standard of accuracy or correspondence.

In logic and philosophy, falsity is closely tied to truth-values. In classical logic, every declarative sentence is assigned a truth-value, typically true or false; falsity is the value opposite to truth. The negation of a true proposition yields a false one, and logically inconsistent forms (such as p and not-p) are themselves false. In formal systems, falsity is sometimes represented by a constant such as ⊥ or F.

Falsity can be categorized by domain. Logical falsity concerns the correctness of inference or form (a contradiction). Empirical falsity concerns claims about the world that evidence or observation contradicts. Semantic falsity concerns the truth conditions of sentences within a language or theory. Moral falsity refers to statements that are deliberately deceptive or knowingly contrary to ethical norms, though moral evaluation can depend on intent and context.

Falsity is a central notion in discussions of truth, belief, justification, and evidence. It plays a key role in semantics, epistemology, and logic, as well as in practical fields such as law and journalism. See also truth-value, negation, and deception.