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Old 03-26-2010, 02:37 AM
Tyrrell McAllister Tyrrell McAllister is offline
Join Date: Jan 2007
Posts: 121
Default Re: Science Saturday: Who Got What Wrong? (Jerry Fodor & Elliott Sober)

Originally Posted by Bloggin' Noggin View Post
It takes a very long time to finally get to the nub of the argument -- which occurs about here. I might almost recommend that people who haven't seen the diavlog start by watching this clip and then proceed to the whole thing.
That's probably Fodor's most direct statement of his conclusion. But most of the diavlog was spent circling around Fodor's key argument for his conclusion. Fodor stated this argument most concisely in these 73 seconds.

Fodor's argument makes an entirely valid point, one which Sober never seemed to grasp fully. However, Fodor's valid point is entirely uncontroversial once it's properly understood. It certainly doesn't imply his conclusion.

Fodor's valid point is this: Natural Selection Theory (NST) requires some causal statements as inputs. It can't generate these inputs by itself. It therefore depends on theories outside of itself to generate these inputs. Such theories include chemistry, geology, and biomechanics. Furthermore, these theories contain no teleology in any sense. That is, they involve no concept that could reasonably be called "purpose".

For example, the theory of chemistry explains two properties of chlorophyll:

(1) Chlorophyll makes plants green.

(2) Chlorophyll undergoes charge separation when exposed to light.

Moreover, the theory of chemistry asserts that it is the charge separation, not the greenness, that causes CO2 to reduce to sugars. That is, chlorophyll makes plant food because of property (2), not property (1). Add some physics ("reproduction requires energy") and some genetics ("containing chlorophyll is a heritable trait"), and you arrive at the statement that chlorophyll helps a plant to make other plants with chlorophyll because of property (2), not property (1).

NST played no part in generating this statement. Rather, NST uses this statement as input to generate the following statement: Plants the world over contain chlorophyll because it has property (2), whereas property (1) was just a "free rider". But NST needed an external theory (chemistry) to determine which property was the free rider. NST couldn't do this on its own.

[ETA: I don't think that Sober ever conceded this. His only reply that I heard was that Fodor had too restrictive a conception of NST. That may be true. But, even under its most expansive conception, NST still needs inputs from other theories to get off the ground. So Fodor is right on this point.]

That is all true. But Fodor draws an invalid conclusion. He believes that NST is itself almost vacuous, that it adds virtually nothing to its inputs, and that, in particular, it adds nothing that could ground assertions about the purpose of a phenotypic trait.

Fodor's error is to ignore what NST does after it receives its inputs from the other theories. The inputs to NST are causal claims about a phenotypic trait's effect on the individual. The contribution of NST is to generate causal claims about the distribution of the phenotypic trait in the population.

For example, teeth can pierce a shell, a harder shell can deflect the teeth, sharper teeth can pierce that harder shell, and so forth. Moreover, it's the sharpness of the teeth that causes the puncturing of the shell, not their whiteness. And it's the hardness of the shell that protects it, not its odor. Theories such as physics tell you this, not NST.

But you need NST to understand evolutionary arms races, where the predator's teeth cause the prey's shell to get harder, which causes the predator's teeth to get sharper, which causes the prey's shell to get even harder, . . . and so on. Sharpness and hardness were singled out by the other theories. But once that's done, NST explains — and predicts! — the effects on the populations over time.

And how does NST justify talk about purpose? As follows:

NST says that certain traits are widespread in a population now because they have certain effects that helped past members of the population to reproduce. (Again, other theories singled these traits out and described their effects, but NST deduces from this their distribution in the population.) To repeat, NST says that these traits exist because they have those particular effects.

That sounds an awful lot like a teleological explanation, but NST gives it a perfectly naturalistic meaning that doesn't presume the existence of any forward-looking agent. And since NST gives this teleological explanation a respectable materialist foundation, NST also allows us to speak of "purpose" without supposing the prior existence of a purpose-formulating mind. We are justified in saying "The purpose of those traits is to have those particular effects."

Last edited by Tyrrell McAllister; 03-27-2010 at 03:06 PM..
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