Suppose somebody has a false intuition about an a priori matter. Is she justified in believing its content? Many plausible answers, of course, will begin with "it depends...". On what does it depend?
Ernie Sosa thinks that among the things upon which it depends is whether the false intuition derives from "some avoidably defective way"; such errors constitute "faults, individual flaws, or defects." (I think Sosa means these two quoted bits to be approximately equivalent, or at any rate, to apply together in the relevant cases.) Sosa thinks this is what is going on when somebody follows her strong inclination to affirm the consequent, inferring from q and (if p, q) to p. By contrast, "the false intuitions involved in deep paradoxes are not so clearly faults, individual flaws, or defects. For example, it may be that they derive from our basic make-up, shared among humans generally, a make-up that serves us well in an environment such as ours on the surface of our planet."
So Sosa's line is that false intuitions do not justify when they derive from faults, flaws, and defects, but do justify when they derive from our basic make-up and are generally shared among humans. I'm suspicious that this distinction will hold up to scrutiny. I think there may be an equivocation on the relevant kinds of 'faults,' 'flaws,' and 'defects' going on. In one sense, of course, one is flawed by virtue of being incorrect; beliefs are supposed to be true, so if one goes wrong, that constitutes some sort of defect. This, of course, cannot be what Sosa has in mind. Instead, he seems to be imagining flaws as deviations from some sort of imperfect but generally effective strategy for getting around in the world. This is, perhaps, the more ordinary sense of a defect. My computer, even when it is working properly, will occasionally crash; a tendency to crash constitutes a defect only when it is not working properly. And maybe there is a good reason why humans ought to have tendencies to accept, for instance, naive set theory.
The problem for this line is that there is also plausibly sound reason for humans to have tendencies to commit more obvious errors, like affirming the consequent. Given the environments we face, having a tendency to affirm the consequent will help us to recognize patterns and confirm hypotheses; inductive reasoning generally looks a bit like affirming the consequent. Similarly with other standard errors; they derive from heuristics that are generally helpful.
So we face a dilemma for upholding Sosa's distinction. Do we say that these errors — these false judgments arising from generally good heuristics — constitute defects or not? If not, then they are relevantly like Sosa thinks the intuitive premises involved in deep paradoxes are. If so, what makes them so, and why should they not apply also to the cases of the paradoxes?
Consider three people. First, the possible über-rational being who looks at me the way the fallacious gambler now looks to me. She describes us both as defective; as failing to live up to the standards of rationality. She can see that I am not tempted by one particular error (the gambler's fallacy) — but also that I regularly commit another (fallacy X), and have some attraction to a third (naive set theory). Second, myself: I think of the fallacious gambler as defective, but of myself and my peers, I think our attraction to naive set theory as nondefective; my more ignorant peers who have not studied philosophy, I even consider justified. (We will suppose I have Ernie's views.) Third, the gambler himself, who accepts his characteristic fallacy and naive set theory alike, and sees no defect in any of us. He considers himself justified in both cases.
All parties agree that the gambler is wrong; he proceeds in a defective way inconsistent with intuitive justification. But Ernie thinks I'm importantly different from him. Ernie thinks that I am not defective, but merely have some tendencies to affirm falsehoods that derive from my general human nature. Our rational superior, presumably, thinks of me as defective in just the same way as the gambler, but to a lesser degree. Does Ernie give any reason we should think her wrong about this?