  Thus there is no need for explicit use of Ockham's Razor as in Smart (1959) though not in Place (1956). (See Place 1960.) Lewis's paper was extremely valuable and already there are hints of a marriage between the identity theory of mind and so-called ‘functionalist’ ideas that are explicit in Lewis 1972 and 1994. In his 1972 (‘Psychophysical and Theoretical Identifications’) he applies ideas in his more formal paper ‘How to Define Theoretical Terms’ (1970). Folk psychology contains words such as ‘sensation’, ‘perceive’, ‘belief, ‘desire’, ‘emotion’, etc. which we recognise as psychological. Words for colours, smells, sounds, tastes and so on also occur. One can regard common sense platitudes containing both these sorts of these words as constituting a theory and we can take them as theoretical terms of common sense psychology and thus as denoting whatever entities or sorts of entities uniquely realise the theory. Then if certain neural states do so too (as we believe) then the mental states must be these neural states. In his 1994 he allows for tact in extracting a consistent theory from common sense. One cannot uncritically collect platitudes, just as in producing a grammar, implicit in our speech patterns, one must allow for departures from what on our best theory would constitute grammaticality.