There is also a parallel with the three interlocking systems of language
distinguished by Halliday (1978), consisting the forms, meanings and functions of
language. In the sociology of mathematics, Restivo (1985) distinguishes the syntactical
and semantic properties of an object (following Hofstadter), paralleling the syntax-semantics distinction. Hersh (1988) makes an analogous distinction between the
‘front’ and ‘back’ of mathematics. Restivo (1988) also distinguishes between ‘social’
and ‘technical’ talk of mathematics, paralleling the distinction between the third level
of pragmatic considerations and the first two levels taken as one, respectively. Thus
precursors of these three levels, in various forms, are to be found in the literature.