PUTNAM’S THEORY OF NATURAL KINDS AND THEIR NAMES IS NOT THE SAME AS KRIPKE’S IAN

Philosophers have been referring to the “Kripke–Putnam ” theory of natural-kind terms for over 30 years. Although there is one common starting point, the two philosophers began with different motivations and presuppositions, and developed in different ways. Putnam’s publications on the topic evolved over the decades, certainly clarifying and probably modifying his analysis, while Kripke published nothing after 1980. The result is two very different theories about natural kinds and their names. Both accept that the meaning of a natural-kind term is not given by a description or defining properties, but is specified by its referents. From then on, Putnam rejected even the label, causal theory of reference, preferring to say historical, or collective. He called his own approach indexical. His account of substance identity stops short a number of objections that were later raised, such as what is called the qua problem. He came to reject the thought that water is necessarily H2O, and to denounce the idea of metaphysical necessity that goes beyond physical necessity. Essences neve