Psychopathologists have been arguing forever about whether psychiatric syndromes are some variety of “biological,” “genetic,” or “brain disorders.”This argument has been hobbled by the lack of a coherent theory of what it means for a complex behavioral entity to be biological, or what the alternative to being biological might be. In the absence of a well-articulated theory, there has been a tendency to assume that the question at issue is whether or not behavioral entities are correlated with chemical, neurological, or genetic variables; and since the answer to this question is always affirmative, the consensus has generally been to move psychiatric syndromes farther and farther down the hierarchy of the sciences. I make the case that questions of whether complex behavioral categories correlate with physical ones is misplaced. Instead, I suggest that questions about the proper location of entities involve determining the level at which the entity is most clearly defined; at other levels the entity is out of focus: detectible but blurry. Blurry entities are poor candidates for successful scientific analysis.