Someone who claims to be a "friend" makes me aware that others are joining Alvin Plantzinga and Gene Callahan on the side of Thomas Nagel's creationists--those claiming that we reason and we know we reason like winged angelic reasoning beings with transcendent access to objective reality, rather than like jumped-up monkeys using error-prone Humean heuristics on brains evolved to improve our reproductive fitness, and hence we know that Darwin is wrong on the evolution of the human mind.
Steven Landsburg: Unreasonable: Brad DeLong appears to argue here that because pure reason once led him, Brad Delong, to an incorrect conclusion about which direction he was facing, it follows that pure reason can never be a source of knowledge. (If that’s not his point, then the only alternative reading I can find is that Thomas Nagel is guilty of choosing a poor example to illustrate a point that DeLong would rather ridicule than refute.) It would be too too easy to make a snarky comment about how we’ve known all along about Brad DeLong’s tenuous relationship with reason….
[H]ere, for the record… facts… none of them, as far as I can see, accessible to humans via anything but pure reason:
- The ratio of the circumference of a (euclidean) circle to its radius is greater than 6.28 but less than 6.29…
Has anybody ever seen a more complete case of self-pwnage?
STEVEN LANDSBURG: The ratio π of the circumference of a circle to its radius is such that 6.29 > 2π > 6.28
KARL SCHWARTZCHILD: That's odd. I have been studying this neutron star. The ratio of its circumference to its radius is definitely not your 2π.
STEVEN LANDSBURG: That's because it is not a Euclidean circle!
KARL SCHWARTZCHILD: And how do you know it's not a Euclidean circle?
STEVEN LANDSBURG: Because if it were a Euclidean circle, the ratio of its circumference to its diameter would be π!
KARL SCHWARTZCHILD: And so your demonstration that Darwin is wrong on the evolution of the human mind is simply that you can make "no true Scotsman!" arguments?
I must say, if Steven Landsburg had set out to strengthen my confidence that we reason like jumped-up monkeys using error-prone Humean heuristics on brains evolved to improve our reproductive fitness, he could not have done better than to write his post.
UPDATE: Gene Callahan, too, is not satisfied and returns for more:
Trying to Clear Up DeLong's Muddle for Him: First, let us look carefully at Nagel's example, and see what he is using it to demonstrate….
[S]uppose I observe a contradiction among my beliefs and “see” that I must give up at least one of them. (I am driving south in the early morning, and the sun rises on my right.) In that case, I see that the contradictory beliefs cannot all be true, and I see it simply because it is the case. I grasp it directly.... [W]hen we reason, we are like a mechanism that can see that the algorithm it follows is truth-preserving.... Something has... gotten our minds into immediate conact with the rational order of the world.... Rational creatures can... make up their own minds.... It does seem to be something that cannot be given a purely physical analysis and therefore... cannot be given a purely physical explanation. If I decide, when the sun rises on the right, that I must [not] be driving... south.... I abandon the belief because I recognize that it couldn't be true.... I operate in the space of reasons..."
So Nagel gives us two beliefs: 1) The sun rises in the east (where I am); and 2) I am driving south, which means the east will be on my left. And a fact: But the sun is rising to my right! So Nagel's point is that we cannot continue to hold 1) and 2) simultaneously: "I must give up at least one of them." How could he have said that more plainly?… Now, Brad Delong comes along and says, "What an idiot! [And he really does insult Nagel like that.] Once, I was in that situation, and I had to give up belief 1)!" Ahem. One does not disprove the proposition that one ought to give up at least one of two contradictory beliefs by showing how once, one gave up one of two contradictory beliefs. What DeLong ought to have done is, given that he had made the "heuristic guess" that he had just found one of the great philosophers of our time committing an elementary logical blunder, stopped and said, "Perhaps this here jumped up monkey needs to guess again?" Instead, he took his misreading and ran with it, and now insists on digging deeper and deeper into the mud of heuristic error.
Alas for Callahan, he gets it wrong again.
Nagel does not believe: "the sun rises in the east (where I am)." Nagel believes: "the sun rises on my right".
Thus the two beliefs that Nagel's reason tells him are in conflict are (a) his belief that he is going south, and (b) his belief he sees the sun rising on his right. The choice he gives himself is between concluding that he is going north and concludeingthat he is hallucinating.
Now I understand that Callahan wishes that Nagel were not Nagel but rather some Nagel' who had added a third belief: (c) "I am in a normal place (but there are weird places on earth where the sun rises in a non-standard way)."
But we go to argument with the Nagel we have, and not the Nagel' Callahan wishes we had.
Callahan would presumably say that Nagel was just being sloppy, and that there is actually an unsloppy Nagel' who had made the argument that Callahan wishes he had made, and whose reason does have transcendental access to objective reality, and that we should deal with the argument not of Nagel but of Nagel'.
But Callahan's confusion of the Nagel' he wishes we were talking about with the Nagel who we are talking about demonstrates my big point quite effectively: powerful evidence that Nagel is a jumped-up monkey using wetware evolved to advance his reproductive fitness, rather than a winged angelic reasoning being with transcendental access to objective reality. No?