A Premise

Lingual Usage:

1. A proposition antecedently supposed or proved; something previously stated or assumed as the basis of further argument; a condition; a supposition.
2. (logic) Any of the first propositions of a syllogism, from which the conclusion is deduced.
3. (usually in the plural, law) Matters previously stated or set forth; especially, that part in the beginning of a deed, the office of which is to express the grantor and grantee, and the land or thing granted or conveyed, and all that precedes the habendum; the thing demised or granted.
4. (usually in the plural) A piece of real estate; a building and its adjuncts. (This meaning arose from meaning #3, by owners of land and/or buildings finding the word in their title deeds and wrongly guessing its meaning.)
5. (authorship) The fundamental concept that drives the plot of a film or other story.

Philosophy:

In philosophy and logic, a premise is a statement or proposition that is assumed or asserted to be true and is used as the basis for reasoning or argumentation. Premises serve as the foundation for constructing an argument, and they are intended to support the conclusion. In a deductive argument, the premises are expected to be true, and if they are, the conclusion necessarily follows. In an inductive argument, the premises provide support for the conclusion, but the conclusion is not guaranteed to be true.