Knowing how to

Syntax

Syntactic theory treats ‘knows how to’ in the same way as a range of expressions typified by ‘knows when to’, ‘knows where to’, ‘knows whether to’, knows why to’. It parses them as:

and thinks of the bracketed clause as a transformation of a question to which the subject S is being said to know the (or an) answer.

Just what is this question? There is more than one possibility, since it might be, for example, ‘Where can one. . . ?’ or ‘Where can I. . . ?’. For this reason syntactic theorists think of the bracketed clause as containing a silent (‘phonologically null’) pronoun governed by the convention that in the standard infinitive construction (‘. . . how to swim’, ‘. . . where to find a decent beer’) always refers to the subject S of the verb ‘knows’. This gives rise to the possibility that in non-infinitival constructions the silent pronoun may break its silence and appear in the form of a pronoun, proper name or other referring expression, as in ‘S knows / where Fred gets his beer /.  . . how Mabel dances a tango’. So sentences of this kind become classifiable syntactically with those using the infinitive. Everything speaks in favour of regarding ‘S knows how to A’ as having the same syntactic shape as ‘S knows that p’ – not as consisting of a clause ‘S knows how to’ and an expression denoting an action, but as a clause ‘S knows’ applied to something much more nearly propositional, namely a transformation of a question.