Zemach's arguments have gone to show that terms might be rigid designators in ordinary language even though they are not natural kind terms. It has been argued that his argument is inconclusive. However it has been claimed that Putnam's argument is much too strong for it would preclude interesting scientific hypotheses about identity between what appear to be different substances, solely on the grounds of modal necessity.It has been shown that rigid designators can be disjunctive but that this possibility is (...) not a foregone conclusion, as Zemach would have us believe. We have to allow for differences between how wesingled out the extension of a natural kind termin the past and how we intend to single out such extensionin the future. Language is not inherently conservative. There is much room for reformist manoevres. *** DIRECT SUPPORT *** A0985038 00002. (shrink)

PREFACE This essay developed from ideas in my doctoral thesis submitted to the Hebrew University in 1977. Chapter three has been amended as regards one of ...