 There is a world of difference between the technical and everyday meanings of the word ‘mechanical’. In technical usage, the term ‘mechanical’, like the term ‘computable’, is tied to effectiveness, and in the technical literature ‘mechanical’ and ‘effective’ are usually used interchangeably (Gandy 1988 outlines the history of this use of the word ‘mechanical’). For example, statements like the following are to be found: