Written by one of today''s most creative and innovative philosophers Ruth Garrett Millikan this book examines basic empirical concepts; how they are acquired how they function and how they have been misrepresented in the traditional philosophical literature. In a radical departure from current philosophical and psychological theories of concepts this book provides the first in-depth discussion on the psychological act of reidentification. It will be of interest to a broad range of students of philosophy especially those interested in the application of evolutionary theory to analytic philosophy.