Thursday, June 26, 2008

Purpose and evolution: a sketch of an argument

Ancient pre-history is not directly relevant to the question of what medical procedures are now morally appropriate. Whether eyes are for seeing is directly relevant to the morality of medical procedures—for instance, it directly affects whether a doctor should agree to blind a patient who wants to be blind. Therefore whether eyes are for seeing is not something that reduces to facts about evolutionary history.


Anonymous said...

Things exist. People ascripe "purpose" to them. Sometimes more aptly than otherwise, but there is no Platonic purpose of things waiting to be discovered.

Enigman said...

Hmm... I would want to conclude that the first premise was false, and explain away any intuition I had that it was true (e.g. distant contingent facts are irrelevant).

Anyway, it is false because ancient pre-history could have included stuff like the Fall, which might have been directly relevant (e.g. by determining our current biology). I only need the possibility for the falsity of the premise.

(Incidentally, bloggers now have this:)

Alexander R Pruss said...

Once one starts on the road of explaining away whole expanses of our perceptions of the world (the moral, the purposeful, etc.), it is hard to stop. One can likewise explain away our perceptions of the past (say, on the hypothesis that this is the first moment of time and it includes false memories), of laws of nature, etc. And then one undercuts science, too.

The Fall only indirectly affects medical ethics, by the intermediary of how we, in fact, now are. Likewise, how I got an injury only indirectly affects what treatment is medically appropriate--if two different causes were to produce the same injury in two patients and the patients were to have the same habits, the same treatment would be medically appropriate.

Anonymous said...

"Once one starts on the road of explaining away whole expanses of our perceptions of the world (the moral, the purposeful, etc.),"

We ascribe purposes to things. We can sometimes do a good job of it, ascribing purposes that to us seem reasonable. Good ascriptions will help us predict other aspects of the thing, and sometimes they will turn out to be reasonable as well. But that doesn't mean we've discovered the "true purpose" of something.

Here is a good example. Humans have good brains that can do multivariable calculus. We might say, the human big brain is for doing multivariable calculus. Or we might say, this big brain let us use tools. Or we might say that the big brain let men produce excellent pick-up lines and woo mates.

All of that is well and good, but there isn't actually a reason or a purpose to the big brain. The descendants of big brain people are alive, the descendants of the small brain people aren't. We can speculate as to the why of that, we can investigate how brain sized develop among humans and proto-humans across generations, but ultimately it is just speculation. Even if it is clever speculation, it doesn't describe any "purpose."

People like to explain things. It is in our nature. We will always come up with the best explanation we can for everything. We can't avoid doing it. Sometimes our explanations are more reasonable than other times, but still they are just our explanations.

Rob K said...


People exist and do things. People ascribe tags like "reasonable" or "unreasonable" to some of these actions. It's the sort of thing we're wired to enjoying. But, really, there's no such thing as Platonic reasonableness in the world, waiting to be discovered. People who ascribe "reasonableness" to certain things are just more prone to reproduce themselves, but ultimately, it's just speculation. Sometimes our ascriptions of "reasonableness" are more reasonable (??) than at other times, but they're still just our ascriptions.

Are you equally happy with all this? If not, why not?

Anonymous said...

"People ascribe tags like "reasonable" or "unreasonable" to some of these actions"

People may have purposes, do things with a purpose. I pick up my fork to eat the steak. That is my purpose. The fork was even created by a person for the purpose of eating food, at least I bought it for that purpose.

Sometimes we do things and ascribe purposes to them after the fact, but let's leave that aside.

Now, just because people probably do have purposes, doesn't mean we should project that onto things. Is the flower purple to attract bees? Well, the flower is purple. Purple ones reproduced, apparently. But the purpleness just is. We can try to explain how purpleness of the flower developed, but if we ascribe purpose to it, we are projecting our human thing onto it.

Now, if you want to say God has a purpose, that's well and good. But I'd be very curious to know how you can possibly know His purpose for most things in particular. You might make guesses, but unless you can check with Him, I don't see how you can do anything based on those guesses.

And, of course, one might say projecting human purpose onto God is a form of anthropomorphisizing blasphemy.

Enigman said...

May I butt in on "how you can possibly know His purpose for most things"? The scientific method of hypothetico-deductivism (suitably tweaked to suit the messiness of real life) explains how (in broad brush-strokes), surely?

It is good that good things exist, so we only require explanations of bad things, as a rule (of rationality), e.g. only philosophers wonder why the sky is blue, but it is only natural to wonder why fire falls from the heavens (when it does). And a good God would have made us to be good, our deepest motives in accord with his...

So our intuitions about his purposes--if suitably informed by the scientific facts available, and if sufficient care is taken (a rider that applies to anything really)--may be rationally expected to be a good indication of what his purposes broadly are.

Anonymous said...

"So our intuitions about his purposes... may be rationally expected to be a good indication of what his purposes broadly are."

Exactly the point of the Book of Job! ;-)

Alexander R Pruss said...

Rob's parody, of course, can be repeated with a lot of other concepts. We have the same kind of reason to think that we are hardwired to ascribe existence, causality, etc. to things outside of us as we do to think that we are hardwired to ascribe purpose there.