Wednesday, August 15, 2007

Aristotle Vindicated Again

The latest issue of Nature (08/16/2007) has an interesting cover headline: "Form Finds Function" introduces an article by Johannes Hermann called "Structure-based activity prediction for an enzyme of unknown function" that argues, in effect, that the function of a certain enzyme can be predicted on the basis of its underlying structure. This is an interesting finding to Aristotelians, who think that there are such things as essences in nature that do, in fact, determine the functions of things.

It also reminds me of a rather interesting factoid that I only learned about because my wife is a crime-novel buff. It seems that there is a certain compound that is often used in cough-syrups called dextromethorphan. This compound is identical to another, called levomethorphan, in every way except one: dextromethorphan twists to the right (hence the "dextro" part of its name) but levomethorphan twists to the left. Apart from the direction of their twisting they are indiscernible. Oh, actually, there is one other difference between them: dextromethorphan relieves your cough, but levomethorphan can kill you if you take too much of it. One is antitussive at low doses and dissociative at high doses, the other is an opiate that relieves pain at low doses and kills at high doses. That's why these compounds figure in crime novels: because they are chemically identical they cannot be distinguished when they are in your body doing things to you, so somebody who had access the the left-leaning molecule could kill you without being caught. I told you leftists were dangerous.

To make a long story short, it seems that we have some grounds here for thinking that strictly reductive, materialist accounts of systems are insufficiently explanatory of mechanism: form is also a necessary component of a full explanation.

7 comments:

Michelle said...

Ah...this is a fascinating area of science and geometry! The molecules themselves are not twisted, they bend polarized light passed through their solutions right (dextro) and left (levo). The molecules are identical, but mirror images (like your hands). The phenomenon is called chirlity (for reasons both you and Aristotle could likely intuit).

So much biological activity depends on whether a molecule is right handed or left handed. My favorite example is spearmint/caraway. The oil primarily responsible for the scent is identical in each, but for being the mirror image. Yet the tastes are so different!

Michelle said...

p.s. I'm chagrined...there's a typo in the previous comment: chirality not chirility! Blame a sticky keyboard (on holiday by the sea shore)...

cnb said...

I'm genuinely perplexed. If the function can be predicted on the basis of form, wouldn't it be a case of "Function follows Form"?

I'm reading "follows" as "comes after", as in "is a consequence of".

Scott Carson said...

Michelle

That spearmint/caraway example is interesting--do you know if they are identical right on down to the molecular composition? Taste, like other similar secondary properties, seems to be principally a function of some sort of supervenience base (such as the molecule) and the human sensory apparatus.

Scott Carson said...

CNB

You're right, but I think the idea is probably just to tag on to a popular cliche and go from there. Unless what they're thinking is that the two things are mutually entailing, but that seems a little too formal.

Scott Carson said...

cnb

Another problem, which I only just noticed (and corrected in the post), is that the cover reades "Form Finds Function", not "Form Follows Function." It looks like I was the one who just followed the old cliche!

My apologies for the confustion!

CrimsonCatholic said...

This reminds me that metaphysics is (ironically) worst known because it is best known. In one sense, Aristotle's position should be the most obvious thing in the world, but the fact of existence is so familiar that one reflexively doesn't think about it.