Does natural selection explain why individual organisms have the traits that they do? This question has been the subject of vigorous debate in recent philosophy of biology. Sober and Walsh have defended the thesis that natural selection does not explain why any individual organism has the traits that it does. This thesis, I shall call ‘the Negative View.’ Neander and Matthen have defended the contrary thesis, which I shall call ‘the Positive View,’ according to which natural selection at least sometimes does explain why an individual organism has the traits that it does. In this paper, I will argue that recent arguments for the Positive View fail for a reason hitherto unnoticed and I will demonstrate that other recent defenses of the Negative View depend upon my own for their plausibility.
I begin, in Section II, by showing that the issue is whether or not natural selection explains, of an individual, why it has the traits it does.