A premise or premiss is a statement that an argument claims will induce or justify a conclusion.
In logic, an argument requires a set of (at least) two declarative sentences (or Proposition) known as the premises or premisses along with another declarative sentence (or "proposition") known as the conclusion. This structure of two premises and one conclusion forms the basic argumentative structure. More complex arguments can use a sequence of rules to connect several premises to one conclusion, or to derive a number of conclusions from the original premises which then act as premises for additional conclusions. An example of this is the use of the rules of inference found within symbolic logic.
Aristotle held that any logical argument could be reduced to two premises and a conclusion. Premises are sometimes left unstated in which case they are called missing premises, for example:
It is evident that a tacitly understood claim is that Socrates is a man. The fully expressed reasoning is thus:
In this example, the independent clauses preceding the comma (namely, "all men are mortal" and "Socrates is a man") are the premises, while "Socrates is mortal" is the conclusion.
The proof of a conclusion depends on both the truth of the premises and the validity of the argument. Also, additional information is required over and above the meaning of the premise to determine if the full meaning of the conclusion coincides with what is.
For Euclid, premises constitute two of the three propositions in a syllogism, with the other being the conclusion.
A premise can also be an indicator word if statements have been combined into a logical argument and such word functions to mark the role of one or more of the statements.