The art of thinking · Philosophy and logic
First principle (philosophy)
Also known as: Archē, Arche
In philosophy and logic, a first principle is a basic proposition or assumption that is not deduced from any other proposition within a system of reasoning and from which further knowledge is derived; Aristotle called such starting points archai.
- Thinking models
- Philosophy
In one sentence
A first principle is a basic proposition not deduced from any other, from which further knowledge is derived — Aristotle’s archē.
Example
In Aristotle’s logic, the principle of non-contradiction — a thing cannot both be and not be in the same respect at the same time — is a first principle: it is not proven, every proof presupposes it.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Origin of the word: Earlier Greek thinkers used archē (beginning, origin) for the original stuff of all things; Thales is reported to have named water. Aristotle made the word a term of logic and science: the starting point "from which a thing is known" (Metaphysics V.1).
- Aristotle's requirements: In Posterior Analytics I.2 the premises of scientific knowledge must be true, primary, immediate, better known than, prior to and explanatory of the conclusion. First principles cannot be demonstrated; according to Posterior Analytics II.19 they are grasped through induction from experience and understanding (nous).
- Today: The phrase lives on in mathematics (axioms), physics (first-principles calculations) and in first principles thinking as a problem-solving method.
- Technical documentation: The equivalent of a first principle in a manual is the statement everything else depends on — the intended use, the basic way the product works, the fundamental distinction the reader must grasp first.
First principle vs. axiom
For Aristotle, axioms are the principles common to all sciences, while each science also has its own principles. In modern mathematics an axiom is a first principle of a formal system that is laid down rather than claimed to be self-evident. The context card How first principles thinking evolved follows the concept from Aristotle to today.
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