In point of fact, Thomas writes about 1/9 of the Supreme Court opinions and deals with about 1/9 of the other legal work (motions, etc), as would be expected of a body with nine members.

My understanding was that Thomas only writes his fair share when you include all his idiosyncratic one-man dissents which influence no one and have failed to move the Overton Window. Is that wrong?

I can't speak to behind-the-scenes influence.

Kind of important a thing to leave out in a political role like that of the nine.

As a lawyer, I don't think any of the current Justices has historically notable intellectual influence except Scalia (Rehnquist also was unusually influential, by he is no longer on the court). Speaking of which, neither Rehnquist nor Scalia are outside the mainstream of American legal thought. Their legal theories are notably on the conservative side, but well within the current Overton window of legal thought.

Gee, I wonder why. Could it have something to do with Rehnquist and Scalia's opinions actually being more persuasive, as I already suggested?

Personally, I am not bothered by Thomas's originalism, as you seem to think; if I had to classify myself, I'd have to admit to considerable sympathy with his positions as I've noted in the past on LW (I think, possibly I argued it elsewhere), originalism is the only position which makes any kind of sense, and the attempts to move away from it and reinterpret it as liberals wish reflects the fact that the Constitution is atrociously outdated and irrelevant because the updating mechanisms have failed completely due to the continual growth of the USA. (When was the last Constitutional amendment which mattered? Do you expect to see another meaningful amendment in your lifetime? I don't.) But the American political system is unable to acknowledge this or come up with any solution, and so we get absurdities like the Supreme Court saying the Constitution protects a right to gay marriage or trying to ban the death penalty, which makes about as much sense as saying the Bible or the Koran protect a right to gay marriage or disapprove of the death penalty.

What I am bothered by is his apparent failure to contribute much to the Court in asking questions to get to the heart of issues, mold or at least influence the thinking of his peers, and influence the majority opinions which matter. A justice who neither is influenced nor influences is a waste of space, and even harmful - like IE6 or Google's neglect of Google Reader. In contrast, I much prefer to read Rehnquist or Scalia's opinions because they were not so blind or irrelevant.

I'm skeptical whether many 100 IQ students could create a career path like Thomas' path.

I'm sure they couldn't, at least not without extenuating circumstances like very able aids or an extremely gross imbalance of verbal and other skills. (IQs are just of the general factor, individual skills can be much higher or lower than the mean; someone can write very well even if they wouldn't understand a statistic if it bit them on the arse.)

But Thomas could easily be one of the 80k that the normal distribution implies, or be a bit below, maybe 97th or 98th percentile or something, which increases the numbers of candidates substantially (more than 3x) while still being plausible. (When I look at thresholds on IQ and characteristics broken down by deciles, I get the impression that for anything which is a fraction of a standard deviation, it is more a difference of quantity than quality; someone 1/3 or 2/3 SDs lower can do just about anything the other person can do, but with more time and effort, perhaps, while at 1 SD it starts to seem like there are things the lower person just won't get with any reasonable amount of time/effort. So a lot of 130 is just plain out of reach for 100, but not for 120.)

As well, the normal distribution is rarely exactly true; for example, when it comes to intelligence, very rare or de novo mutations mean there is an excess of retarded or very disabled people than the calculations would predict, because one mutation in the wrong place can break a mind, and there are a few phenomenon which might create little bumps in the black tail as well - most obviously, given your mentioned examples, immigrants from Africa or the Caribbeans, but a few other things like assortative mating might also happen.