What the Argument Does Not Show

Ayer's work is motivated by a version of traditional questions raised by the argument from illusion. He, in a sense, accepts a conclusion of the argument from from illusion. However, he denies the validity of the argument in its traditional form and essentially all the consequences that have been taken to follow from it. Today, we look at the most prominent examples.

The world of sensible phenomena is self-contradictory

(Bradley, British idealist) The claim that the world of sensible phenomena is self-contradictory, taken literally, doesn't even make sense. What is a contradiction? It what obtains between a truth-bearer and its denial. Here is contradiction:

• This coin is round.
• This coin is not round.

"Sensible phenomena," whatever they are, are not truth bearers. That is, they are not the kinds of things that are true or false, that can be denied, and so forth.

Perhaps there is some metaphorical use of "self-contradictory" being employed here. If there is, there is no agreed-on explanation of what is being claimed. The closest claim that makes literal sense is the claim that our descriptions of the world of sensible phenomena contradict each other.

Here is an example:

• The coin looks round.
• The coin looks not round.

There is, of course, in a certain dumb interpretation, a contradiction here. But no one is confused or takes that "contradiction" seriously:

• When I look from here, the coin looks round.
• When you look from there, the coin looks not round.

There is a certain way of describing sensations that leads to spurious contradictions. So, obviously, we shouldn't talk that way. But we don't.

Perhaps the thought is that if the coin looks round, it must be round, and so we have the contradiction

• The coin is round.
• The coin is not round.

That is, perhaps, the best argument one can make for the claim, but who ever thought (except for a few confused idealists) that things must always be as they appear?

Our ideas of qualities are not resemblances of any qualities of material things

There is (slightly) better use of the argument from illusion to conclude that we have no reason to believe that things really are ("in themselves") as our senses tell us they are.

A round coin sometimes looks ellliptical, and so the evidence of our senses about how things are is not always correct, and is, therefore, never completely trustworthy. We can therefore never get any evidence that or reason to believe that our senses are ever correct. We have no reason to believe that things are as we perceive them.

Worse, forget about whether we are getting the colors wrong, we have no reason to think that things are actually colored at all:

• To see the "real" color of something, one needs good eyes, a functioning mind, an unobstructed view, and good light. The "color of an object" depends on far more than just the object. If it is the color of anything, it is the color of object+light+view+eyes+mind.
• We can explain why an object appears to have the color it does appear to have, in every case (good light, no light, colored light, good view, view through rose-colored lenses, view to someone who is color blind, …) without ever mentioning anything that has color.

Primary vs secondary qualities

Locke. Certain qualities (shape, extension, number) play a central explanatory role in our physical theory of perception. Those are primary qualities. Other qualities (hot or cold, color, rough or smooth) are explained solely in terms of the primary qualities. If things don't really have the secondary qualities, our explanations of why they seem to will go through without change. We have no evidence that things have secondary qualities.

Traditional argument: the thing itself is not colored. (Just look at it in the dark.) No color appears except to an eye. The eye itself is not colored. (Just look at it in the dark.) There is no color.

Unfortunately for Locke, the argument works just as well for primary qualities (qualities that can be measured quantitatively). Why didn't he draw that conclusion? Everyone has, subsequently.

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What is wrong with the argument, according to Ayer? Why shouldn't properties of things that are dependent on appropriate conditions really be properties of the things? No argument has been given. In order to claim that the dependent properties are sometimes properties of things, we need to find a way to separate veridical perceptions (of real properties) from other perceptions.

Supposing that that problem can be solved, why don't, for example, blue things always look blue. Ayer's answer is that what it is for a feather to be blue is that it has the following property:

• If seen in good light with an unobstructed view by a normal eye, the feather will look blue.

That all makes perfect sense provided (35) a thing itself is nothing apart from its actual and possible appearances. But that is a giant if. Ayer endorses that, and so we should look at whether that is tenable, whether it is needed, and how Ayer can claim not to be an idealist while endorsing it.

We are deceived by our senses

Being "deceived by our sense" makes about as much sense as our senses being self-contradictory: One clear requirement for having been deceived is having believed something false. Truth bearers are necessary for deceit. (Or something like that.) We only get deceived by drawing conclusions on the basis of what we have sensed.

Inductive vs deductive logic

We draw conclusions on the basis of reasoning, and reasoning is traditionally divided into two kinds. (There are more.)

Deductive reasoning from premises (prior beliefs) to a conclusion is reasoning such that if the premises are true, the conclusion must be true.

Example:

Socrates was a philosopher.
All philosophers are mortal.
Therefore,
Socrates was mortal.

But if that were the only kind of reasoning we engaged in, we wouldn't get far. Sometimes, all other reasoning is called inductive. Sometimes (as with Ayer) only reasoning of the sort exemplified below is called inductive, but that usually (as with Ayer) goes with the belief that all reasoning is some compound of deductive reasoning with reasoning of the kind in the example.

Example:

It didn't snow in Tucson on 1 January 1900.
It didn't snow in Tucson on 2 January 1900.
.
.
.
Therefore,
It never snows in Tucson.

The traditional example in 20th century Anglo-American philosphy concludes that all ravens are black.

Inductive reasoning has two characteristics that are most important for our purposes:

1. It is based on experience.
2. It is not perfectly reliable.

We are, in fact, very rarely deceived in the conclusions we draw based on the evidence of our senses. We are deceived from time to time—our senses aren't perfectly reliable. But no one until Descartes ever thought that they should be. We have good reason to believe, based on our perception, lots of things. Are we absolutely certain of such things beyond all possible doubt? No. Is there anything surprising or worrying about that? No.

Ayer says (45) "we can never be certain that any of the propositions in which we express our perceptual judgements [_sic_] are true, but rather that the notion of certainty does not apply to propositions of this kind."

-- ShaughanLavine - 23 Jan 2007