Philosophical logic

Nominalism is a metaphysical view in philosophy according to which general or abstract terms and predicates exist, while universals or abstract objects, which are sometimes thought to correspond to these terms, do not exist.

Antinomy (Greek ἀντί, antí, "against, in opposition to," and νόμος, nómos, "law") refers to a real or apparent mutual incompatibility of two laws.

Kripke semantics (also known as relational semantics or frame semantics, and often confused with possible world semantics) is a formal semantics for non-classical logic systems created in the late 1950s and early 1960s by Saul Kripke and André Joyal.

For example, in arithmetic, it allows the expression of the statement that every natural number has a successor.

A sign is an object, quality, event, or entity whose presence or occurrence indicates the probable presence or occurrence of something else.

A lie is a statement that the stating party believes to be false and that is made with the intention to deceive.

In linguistics, meaning is what the source or sender expresses, communicates, or conveys in their message to the observer or receiver, and what the receiver infers from the current context.

Broadly, any metalanguage is language or symbols used when language itself is being discussed or examined.

In metaphysics, the problem of universals refers to the question of whether properties exist, and if so, what they are.

Rationality is the quality or state of being reasonable, based on facts or reason.

The problem of induction is the philosophical question of whether inductive reasoning leads to knowledge understood in the classic philosophical sense, since it focuses on the alleged lack of justification for either:

Rigour or rigor (see spelling differences) describes a condition of stiffness or strictness.

Intensional logic is an approach to predicate logic that extends first-order logic, which has quantifiers that range over the individuals of a universe (extensions), by additional quantifiers that range over terms that may have such individuals as their value (intensions).

A non-linguistic meaning is an actual or possible derivation from sentence, which is not associated with signs that have any original or primary intent of communication.

The philosopher Immanuel Kant uses the terms "analytic" and "synthetic" to divide propositions into two types.

In epistemology, criteria of truth (or tests of truth) are standards and rules used to judge the accuracy of statements and claims.