Elliott Sober''s selection for/selection of distinction has been widely used to clarify the idea that some properties of organisms are side-effects of selection processes. It has also been used, however, to choose between different descriptions of an evolutionary product when assigning biological functions to that product. We suggest that there is a characteristic error in these uses of the distinction. Complementary descriptions of function are misrepresented as mutually excluding one another. This error arises from a failure to appreciate that selection (...) processes can be described at several different theoretical levels. (shrink)