ABSTRACT
It is fair to set up two criteria for assessing theories (particu - larly 'formal' theories) for which the claim is made that they in some way explain behaviour. First, an adequate theory must be capable of producing in a specified way something which corresponds to at least some aspect of behaviour. A small boy on being offered a model car would be direly disappointed on being given something made of clay with wheels that did not even go round. Yet we are offered theories of behaviour which are often even more disappointing: equivalent to a series of tickets joined together with string, and with the tickets bearing legends that might for a model car be 'direction system', 'backfiring inhibitor' and so on. Clearly, many theoretical attempts have no mechanism, no formal set of rules, no criteria, indeed no operations capable of producing anything, let alone events corresponding to behaviour.
