Natural kinds, explanation, and essentialism in chemistry.

The problem of natural kinds in chemistry is analyzed, proceeding mainly from Rom Harré's and Jaap van Brakel's writings. The problem of natural kinds proves to be different in general philosophy and in philosophy of science. This problem, which originally emerged at the borderline of science and philosophy, belongs to the domain of philosophy of science. Philosophy in general cannot hope that scientific knowledge will help to explain philosophical issues. Chemistry has to be taken very seriously in philosophy of science. Not only do empirical arguments indicate that chemistry should be regarded as a typical science, but it is also relevant for elaborating a theoretical model of science. Chemistry as the science of substances is well suited for the philosophical analysis of the role of the concept of natural kinds in science. The viability of the concept of a natural kind in philosophy of chemistry derives from the explanatory role of chemical natural kinds. The problem of explanation in its turn relates natural kinds to the laws of nature and scientific theories, that is, to classical issues in philosophy of science and to discussions on their (supposed) specificity in chemistry. In philosophy of science, one can demonstrate that there exists a third option between metaphysical realism and internal realism (to use Putnam's terminology). According to this third type of realism our "world versions" (including natural kinds identified by us), but not the world itself, are relative to us.