Some people think that there are no species. Moreover, they wrongly think this view is a consequence of evolution and that Darwin himself denied there were any. Now what Darwin thought 150 years ago is of no real consequence to modern biology, but he didn’t think species were unreal constructs; he thought there was no single set of properties species had to have. He was not a taxonomic essentialist. But neither is it the case that species are unreal because they shade into each other. In modern philosophy, there is an ongoing debate over whether one can have vague and fuzzy sets or kinds, but for science we need only a little logic and metaphysics: If we can identify mountains, rivers, and organisms, we can identify species, and they will tend to have a “family resemblance” (Wittgenstein’s most apt phrase in this context).