Aristotle (384–322 BC)

DOI: 10.4324/9780415249126-A022-1
Version: v1,  Published online: 1998
Retrieved September 22, 2018, from

6. Knowledge, science and demonstration

The progress from what is known to us to what is known by nature aims at epistēmē, the scientific knowledge whose structure is exhibited in the demonstrative pattern described in the Posterior Analytics. A demonstration is a deduction in which the premises are necessarily true, prior to and better known than the conclusions, and explanatory of the conclusions derived from them. Aristotle assumes that if I know that p, then I can cite some justification q, to justify my belief that p, and I also know why q justifies p (Posterior Analytics I 2). The right sort of justification relies on things better known by nature – the general laws and principles that explain the truth of p. Since these are embodied in demonstrations, grasp of a demonstration of p expresses knowledge of p. Aristotle’s theory of demonstration, then, is not intended to describe a procedure of scientific inquiry that begins from appearances; it is an account of the knowledge that is achieved by successful inquiry.

To show that a deduction is a demonstration, we must show that its premises are better known than the conclusion. Sometimes we can show this by demonstrating them from higher premises that are even better known. This process of justification, Aristotle claims, must be linear and finite. A circular ‘justification’ must eventually ‘justify’ a given belief by appeal to itself, and an infinite regress imposes on us a task that we can never complete. Since, therefore, neither a circle nor an infinite regress can really justify, a proper justification must ultimately appeal to primary principles of a science.

These primary principles are ‘assumptions’ (hypotheseis); we must see that they are better known and prior to other truths of a science, without being derived from any further principles. Since they are the basis of all demonstration, they cannot themselves be demonstrated; Aristotle claims that we have non-demonstrative understanding (nous: Posterior Analytics II 19) of the ultimate principles of each science (see Nous).

How are we entitled to claim understanding of an ultimate principle? Aristotle believes that the principles of a science are reached from appearances (perceptual or dialectical or both), which are the starting points known to us. He may believe that this relation of the principles to appearances justifies us in accepting them as first principles and in claiming to have understanding of them. This explanation, however, does not easily fit Aristotle’s demand for linear and finite chains of justification. That demand suggests that the assumptions of a science must be self-evident (seen to be true without any inferential justification), so that his conception of knowledge expresses a foundationalist position (see Foundationalism §3). (On difficulties in foundationalism see Agrippa.)

Although Aristotle’s aim of reaching a demonstrative science reveals some of his epistemological doctrines and assumptions, it does not evidently influence most of the structure or content of most of the surviving treatises. In his main philosophical works, the influence of dialectical methods and aims is more apparent.

Citing this article:
Irwin, T.H.. Knowledge, science and demonstration. Aristotle (384–322 BC), 1998, doi:10.4324/9780415249126-A022-1. Routledge Encyclopedia of Philosophy, Taylor and Francis,
Copyright © 1998-2018 Routledge.

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