# Definition:Premise

## Definition

A **premise** is an assumption that is used as a basis from which to start to construct an argument.

When the validity or otherwise of a proof is called into question, one may request the arguer to "check your premises".

## Also known as

Some sources use the word hypothesis, but this tends nowadays to have a slightly different meaning from **premise**.

The word **supposition** is also found.

Some sources use the older (some say archaic) spelling **premiss**, whose plural is **premisses**.

## Also defined as

Some authors use the term **premise** to mean the antecedent of a conditional statement.

## Also see

## Historical Note

In the early days of (mathematical) logic, there was a significant distinction between **premises** on the one hand, and assumptions on the other hand.

**Premises** ought to be essential for the validity of the argument, while assumptions were expected to be discharged at some point in the argument.

Over the years, through abstraction and change of perspective on (symbolic) logic, this distinction is becoming less important; however, it still retains considerable conceptual value.

For example, the Rule of Assumption of natural deduction is a symbolic representation of both these concepts, but allows to distinguish between them to make it easier to convey the overall structure of a proof to the reader.

## Technical Note

When invoking a **premise** in a tableau proof, use the Premise template:

`{{Premise|line|statement}}`

or:

`{{Premise|line|statement|comment}}`

where:

`line`

is the number of the line on the tableau proof where the**premise**is to be invoked`statement`

is the statement of logic that is to be displayed in the**Formula**column,**without**the`$ ... $`

delimiters`comment`

is the (optional) comment that is to be displayed in the**Notes**column.

## Sources

- 1946: Alfred Tarski:
*Introduction to Logic and to the Methodology of Deductive Sciences*(2nd ed.) ... (previous) ... (next): $\S \text{II}.9$: The Use of Implication - 1959: A.H. Basson and D.J. O'Connor:
*Introduction to Symbolic Logic*(3rd ed.) ... (previous) ... (next): Chapter $\text I$ Introductory: $3$. Logical Form - 1964: Donald Kalish and Richard Montague:
*Logic: Techniques of Formal Reasoning*... (previous) ... (next): $\text{I}$: 'NOT' and 'IF': $\S 3$ - 1965: E.J. Lemmon:
*Beginning Logic*... (previous) ... (next): Chapter $1$: The Propositional Calculus $1$: $1$ The Nature of Logic - 1973: Irving M. Copi:
*Symbolic Logic*(4th ed.) ... (previous) ... (next): $1$ Introduction: Logic and Language: $1.2$: The Nature of Argument - 1977: Gary Chartrand:
*Introductory Graph Theory*... (previous) ... (next): Appendix $\text{A}.5$: Theorems and Proofs - 1980: D.J. O'Connor and Betty Powell:
*Elementary Logic*... (previous) ... (next): $\S \text{I}: 1$: The Logic of Statements $(1)$ - 2000: Michael R.A. Huth and Mark D. Ryan:
*Logic in Computer Science: Modelling and reasoning about systems*... (previous) ... (next): $\S 1.2$: Natural Deduction - 2012: M. Ben-Ari:
*Mathematical Logic for Computer Science*(3rd ed.) ... (previous) ... (next): $\S 3.2$: Definition $3.2$