All readings are in Ancient Greek Philosophy, ed. Cohen, Curd, and Reeve

Aristotle's Theory of Knowledge and Demonstration

Posterior Analytics: Highlights Book I

I.1 All teaching and learning result from previous cognition.

(i) We presuppose that something is (the fact); or

(ii) We comprehend what it is (the reasoned fact).

Solution to Meno's Paradox: We know in one way what we are learning, while being ignorant in another way.

I.2 Demonstrative knowledge

Demonstration=a deduction expressing knowledge.

Premises of a demonstration must be true, primary, immediate, better known than, prior to, and explanatory of the conclusion. "better known" and "prior" have two senses:

(i) closer to us, or clearer through sense-perception;

(ii) further from us, closer to the truth (closer to the universal)

I.3 Demonstrative knowledge is necessary, hence must be a deduction from things that are necessary. To understand this necessity, Aristotle refers us to three notions: "belonging in every case," "in its own right," and "universal":

(i) A belongs to B in every case (holds of all cases at all times)

(ii) A belongs to B "in its own right" (kath' hauto):

(1) essence of B is composed of A

(2) B is present in the account revealing what A is

(3) B is not said of A as of another underlying subject

(4) A belongs to B because of itself.

(iii) A belongs to B universally if both (i) and (ii) are true.

I.6 Demonstration must be through a middle term that is necessary.

Brief example of a syllogism:

Comments: The syllogism has two premises and a conclusion. Each premise is a proposition with a subject term and a predicate term. In the conclusion, the subject term is C and the predicate term is A. There is also a "middle term" B, which is the term linking the C's and the A's. Hence Aristotle regards the middle term as what provides the explanation (i.e., B explains why all C's are A's.)

I.10 Some principles are common to different sciences, some are distinctive of a given science.

II.8 Knowing what a thing is = knowing the explanation of what it is.

Example: What is an eclipse? Answer: a blocking of the moon's light by the earth.

Let A=eclipse, B=blocking by the earth, and C=moon.

In this example, asking whether the moon is eclipsed = asking whether B is or is not. We have the "account" of eclipse (namely, B, the middle term), so we learn both the fact (that there is eclipse) and the reasoned fact (why) at the same time.

Alternatively we might only know the fact, not the reason.

Let A=eclipse, B=inability of moon to cast shadows, C=moon.

If it's clear that A belongs to C, then to inquire why it belongs is to inquire into what B is (blocking? rotating? extinguishing?). B is an "account" or explanation of one of the other two "extreme" terms, A (eclipse).

Another example: A=thunder, B=extinguishing of fire, C=cloud. Then we get an account of thunder as "extinguishing of fire in the cloud."

II.10 The "nominal" definition tells what a name signifies (thunder is noise, eclipse of the moon is failure to cast shadows). The "real" definition tells why this is so (thunder is noise due to extinguishing of fire, etc.). The "real" definition is read off from a demonstration (differently arranged).

II.19 All demonstration comes from pre-existing knowledge, knowledge of principles. How do we know these? They are neither innate nor are they acquired from nothing. They must be acquired through a distinctive potentiality we have. This potentiality is sense-perception. The chain goes like this:

Perception -->leads to--> Memory -->leads to--> Experience -->leads to-->Understanding.

From experience derives "understanding" of principles (of crafts or of sciences)

cfreeland@uh.edu

March 14, 1996