A premise is a statement that supports a conclusion in an argument. It is a reason to believe something. In a syllogism, the premises are the two statements that lead to the conclusion. All men are mortal. Socrates is a man. Therefore, Socrates is mortal. The first two statements are premises. The third is the conclusion. Premises can be true or false. They can be supported by other arguments or accepted as starting points. In a valid argument, if the premises are true, the conclusion must be true. In a sound argument, the premises are true and the form is valid.

Premises can be stated or implied. They can be explicit, as in a formal argument, or hidden, as in everyday reasoning. Identifying hidden premises is a key skill in critical thinking. Often, an argument seems convincing because a questionable premise is left unstated. Making it explicit allows it to be evaluated. Premises can also be disputed. If someone challenges a premise, the argument may need to be supported by further argument. In philosophy, premises are often tested by counterexamples and thought experiments. The goal is not to win but to find premises that are true and relevant.

Types of premises

• Major. The broader statement in a syllogism.
• Minor. The more specific statement.
• Implicit. Unstated but assumed.
• Empirical. Based on observation.
• Conceptual. Based on definitions or logic.

A premise is not the same as an assumption, though the two overlap. An assumption is something taken for granted. A premise is offered as a reason.