Definition
A premise is a statement offered as a reason for accepting some other statement — the conclusion. An argument, in the logical sense, is just a structured group of premises together with the conclusion they are intended to support. The premises are not assumed to be true unconditionally; they are the inputs whose truth, if granted, the conclusion is supposed to follow from. Every step in a formal proof and every defensible piece of informal reasoning has the same skeleton: these premises, therefore this conclusion.
Premises divide loosely into two kinds. Some are factual claims — empirical or definitional propositions the reasoner expects the audience to accept. Others are inferential — general principles, rules of inference, or background assumptions that license the move from one factual claim to another.
Why it matters
How it works
Evaluating an argument is a two-stage process. First, the analyst asks whether the conclusion follows from the premises — the question of validity, which is purely structural. A valid argument is one in which the conclusion cannot be false if the premises are true; the form of the inference guarantees the link. Second, the analyst asks whether the premises are in fact true — the question of truth, which depends on the facts of the world, the meanings of the terms, and the background assumptions the argument relies on. Only when both stages pass — valid form and true premises — does the argument count as sound.
Identifying premises in natural-language argument is harder than it looks. Speakers and writers leave premises implicit when they expect the audience to share them; the missing premise is precisely where misunderstandings and manipulations hide. An enthymeme is an argument with one or more unstated premises, and surfacing them is often the most productive move in critical analysis. Once every premise is on the table, the argument can be tested: which premises are factually true? Which are merely plausible? Which are smuggled in to do the work the explicit reasoning cannot? The discipline of reconstructing arguments by stating every premise explicitly is the practical core of logical literacy.