A premise or premiss[a] is a true or false statement that helps form the body of an argument, which logically leads to a true or false conclusion. A premise makes a declarative statement about its subject matter which enables a reader to either agree or disagree with the premise in question, and in doing so understand the logical assumptions of the argument. If a premise is logically false, then the conclusion, which follows from all of the premises of the argument, must also be false—unless the conclusion is supported by a logically valid argument which the reader agrees with. Therefore, if the reader disagrees with any one of the argument's premises, they have a logical basis to reject the conclusion of the argument.
In logic, an argument requires a set of (at least) two declarative sentences (or "propositions") 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.
Socrates is mortal because all men are mortal.
It is evident that a tacitly understood claim is that Socrates is a man. The fully expressed reasoning is thus:
Because all men are mortal and Socrates is a man, Socrates is mortal.
In this example, the dependent 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. These categorical propositions contain three terms: subject and predicate of the conclusion, and the middle term. The subject of the conclusion is called the minor term while the predicate is the major term. The premise that contains the middle term and major term is called the major premise while the premise that contains the middle term and minor term is called the minor premise.
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. It indicates that the statement it is attached to is a premise.
- In general usage, the spelling "premise" is most common; however, in the field of logic, the spelling "premiss" is often used, especially among British writers.
- Audi, Robert, ed. (1999). The Cambridge Dictionary of Philosophy (2nd ed.). Cambridge: Cambridge University Press. p. 43. ISBN 0-521-63136-X.
Argument: a sequence of statements such that some of them (the premises) purport to give reasons to accept another of them, the conclusion
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