W. V. O. Quine is generally seen as one of the foremost empiricists of the twentieth century. For large parts of his career, the label “empiricist” is accurate; in his mature work, however, he integrated decidedly antiempiricist elements in his epistemology. From The Roots of Reference onward, he enlists natural selection and innate cognitive structures to ensure that scientific concepts have a “degree of objective validity.” From From Stimulus to Science onward, he also explains the very possibility of communication via a preestablished harmony of innate cognitive structures that is guaranteed by natural selection. This article reconstrues the reasons that compelled Quine to these commitments, and it details the development of Quine’s thinking on these topics across more than 3 decades; in particular, the article argues that recognizing that so-called stimulus meanings are private decisively shaped Quine’s views. By means of a critical evaluation, the article argues that natural selection can make plausible that scientific concepts have a degree of objective validity—if this Quinean claim is properly understood; in contrast, the article suggests, with recourse to research by Robert C. Richardson, that it is doubtful whether natural selection can underpin the preestablished harmony that Quine requires to explain communication.