Two important thought-experiments are associated with the work of Hilary Putnam, one designed to establish multiple realizability for mental kinds, the other designed to establish essentialism for natural kinds. Comparing the thought-experiments with each other reveals that the scenarios in both are structurally analogous to each other, though his intuitions in both are greatly at variance, intuitions that have been simultaneously well received. The intuition in the former implies a thesis that prioritizes pre-scientific over scientific indicators for identifying mental kinds (...) in certain circumstances, while his intuition in the latter implies a converse thesis, prioritizing scientific over pre-scientific indicators for identifying natural kinds in analogous circumstances. In this paper I question whether we can consistently endorse both of these intuitions. A consideration is presented to attempt to justify the common intuition found in the multiple realization thought-experiment. Then it is argued that this same consideration has application in the structurally analogous Twin-Earth thought-experiment. This recommends a kind of multiple realization thesis for natural kinds, in opposition to a scientific essentialist approach. The various respects in which mental kinds like pain and natural kinds like water are similar to each other, such that similar philosophical treatments are warranted for both, are enumerated. (shrink)

In its original form due to Ian Hacking, entity realism postulates a criterion of manipulative success which replaces explanatory virtue as the criterion of justified scientific belief. The article analyses the foundations on which this postulate rests and identifies the conditions on which one can derive a form of entity realism from it. It then develops in detail an extensive class of counterexamples, drawing on the notion of quasi-particles in condensed matter physics. While the phenomena associated with quasi-particles pass the (...) entity realist's criterion of manipulative success, quasi-particles themselves are illusions, and can be seen to be so even on the basis of the largely non-theoretical "home truths" that one must be ready to admit as background knowledge. Hence, Hacking's entity realism is shown to be incoherent. (shrink)

The “scientific essentialist” doctrine asserts that the following are examples of a posteriori necessary identities: water is H2O; gold is the element with atomic number 79; and heat is the motion of molecules. Evidence in support of this assertion, however, is difficult to find. Both Hilary Putnam and Saul Kripke have argued convincingly for the existence of a posteriori necessities. Furthermore, Kripke has argued for the existence of a posteriori necessary identities in regard to a particular class of statements involving (...) proper names. Neither Kripke nor Putnam, however, has argued convincingly that sentences containing syntactically complex terms or descriptive phrases can express a posteriori necessary identities. I will argue by way of a hypothetical example that ‘water is H2O’ does not express a necessary identity. My argument is unique in that it attacks the relevant sufficiency claim needed to underwrite this putative necessary identity.1 That is, even if we grant that water is necessarily composed of H2O, we should not accept that H2O necessarily forms water. (shrink)