Contingent vs. Necessary Truth in Classical Philosophy

Question

I am reading "Ancient Philosophy" by Anthony Kenny (Vol 1 of his "A New History of Western Philosophy", OUP, ISBN 0–19–875273–3).

I was intrigued by the following statement (p.176):

"However, ancient epistemology is bedevilled by two different but related fallacies. Both of them are generated by a misunderstanding of the truth that whatever is knowledge must be true. One of the fallacies haunts classical epistemology, up to the time of Aristotle; the other fallacy haunts Hellenistic and imperial epistemology."

For the sake of limiting the scope of discussion, my question is about the first fallacy. Here's how Kenny describes it:

"The first fallacy is this. ‘Whatever is knowledge must be true’ may be interpreted in two ways.
(1) Necessarily, if p is known, p is true or
(2) If p is known, p is necessarily true.

(1) is true but (2) is false. It is a necessary truth that if I know you are sitting down, then you are sitting down; but if I know you are sitting down it is not a necessary truth that you are sitting down; you may get up at any moment. Plato and Aristotle, over and over again, seem to regard (2) as indistinguishable from (1). Given the necessary connection between knowledge and truth, they seem to think, only what is necessary can be known. From the acceptance of (2) there flows the construction of the theory of eternal and immutable Ideas, and there flows the impossible ideal of Aristotelian science." (p.176-177)

My question is, what exactly is Kenny saying about Plato's and Aristotle's epistemological views?

I mean, it seems that he's talking about contigent vs. necessary truth, and that Plato & Aristotle thought of all truth as necessary -- but I don't understand what that really means in terms of their theories. Is it being claimed that if Aristotle saw a blue unicorn, he'd assert that all unicorns are necessarily blue? I.e. that he would not be able to conceive of (the truth of) the color as being contingent on the particular unicorn? Or is it being claimed that he'd consider the blue-ness of a specific unicorn to be something less than truth, precisely because this blue-ness is not necessary of other unicorns? Or something else?

Kenny closes by making a strong claim about the "impossible ideal of Aristotelean science". I think here he ascribes to Aristotle the theory that science should be a deductive (via syllogisms) process, producing only "necessary" truths. But is calling it an "impossible ideal" really justified, especially in the sense of Aristotle committing some kind of clear fallacy..? After all, didn't the logical positivists take up exactly this line of thinking about truth, and haven't they come up with some interesting/useful/influential arguments about what science is, even if other approaches have become more popular..?

Answer 1

The basic issue at hand is the location of the necessity or to put it another way -- to what does necessity apply. I don't think it's quite as viscous as your blue unicorn example makes it out to be -- because I think you're jumping from particular to universal in a way that they are not required to do.

To state it a bit more carefully,

I know there is a blue unicorn.

What follows is

1. Because I know there is a blue unicorn, that unicorn is necessarily blue.

BUT NOT

2. Because the unicorn is blue, there is a necessity that this unicorn be blue.

i.e., my knowing fact Q necessarily entails Q is true. But it does not entail Q is necessarily true. The necessity on the modern picture lies squarely on the transitivity from knowledge; the classical picture does not distinguish things so carefully.

Or to put it another way, you could understand Kenny's claim as a claim about the direction of the "arrow of necessity", known things are necessarily true, true things are not necessarily so.

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Added to try to again

It's important to not confuse the issue. Aristotle is not committed to something like this:

1. I know this dog has yellow fur
2. Therefore, all dogs have yellow fur.

He is committed to this:

1. I know this dog has yellow fur.
2. This dog by necessity has yellow fur.
3. Yellow fur is a necessary property of this dog.

Step 2 is trivially true assuming that knowledge is understood as knowing the truth of something (the necessity then would come from the definition).

Step 3 however is not at all trivial and that's where things get messy in ancient vs. modern. Aristotle on several occasions (I don't have the cites with me but think this happens in the Posterior Analytic and Organon and Metaphysics and Biology) seems to commit himself to the claim that 3 is also true.

On the modern account we don't commit ourselves to anything about the metaphysics of the object in question -- just it's current state. And that's what Kenny is making a big deal about.

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I don't know if I've ever read that particular text by Kenny but two things occur to me. It's not like Kenny has no stake in this particular debate; he's got a position that depends on modifying Aristotle/Aquinas quite a bit and in particular with respect to the understanding with form. So it's not surprising that he thinks there is something wrong with Aristotle's belief (in continuity with Plato) that form is immutable.

Two, it does make sense that the task of science would have trouble proceeding if all truths are assumed to be necessary. Contingency is a key feature in being able to test situations and do experiments. For instance, if we had the following:

1. given conditions A,B, and C, then Q.
2. just given A and B, no Q.
3. with just A, Q.

Then this sort of variation requires us not to take the necessity of our knowledge meaning something is true as projecting into the truth of something necessitating it's truth.

That's my best reconstruction having not read Kenny (in general) in a bit.