Kinds, classification and realism

The philosophy of classifications relates closely to the natural kinds problem. This is treated at many levels, since it implies a position on what exists (ontology); how we come to know what exists (epistemology); and the meaning of the terms assigned to what exists (philosophy of language). Classification is a fundamental aspect of science too. Scientific theorization is associated with the development of classification schemes. It is not a coincidence that Kuhn (2000) in his later works tended to replace the idea of paradigm with the notion of lexical taxonomy, i.e. the taxonomic structure projected by scientific theories upon the world. The debate about natural kinds is a central topic of the philosophy of many scientific disciplines, chemistry included. In this short piece, I will not enter into the discussion on the periodic system as a natural classification. The focus will be instead on the question of realism that underlies the natural kind debate and the possibility to maintain a realistic position while acknowledging the role of the observer in how reality is known.