Yet a basic assumption behind a great deal of language teaching is exactly that: if you teach the product, the process will take care of itself. ‘This is an omelette. I cut it in bits. You can see what it looks like from the inside. OK. Are you ready? Now make one!’ This is what I call the ‘Humpty Dumpty Fallacy’. Just to remind you:

All the King’s horses and all the King’s men Couldn’t put Humpty together again.

The language teaching equivalent is: I, the teacher, will cut the language into lots of little pieces – called grammar – so that you, the learner, will be able to reassemble them in real communication.Thus: conjunction if + subject pronoun + past perfect (consisting of past auxiliary had + past participle), followed by nominal that-clause, consisting of... etc, etc.What happens, of course, is that learners take these little bits of grammar description and try to stick them together, and then wonder why they can’t produce sentences like If I’d known you were coming, I would have baked a cake. It ignores the fact that the product and the process are two quite different things – that there is grammar and there is grammaring, and the latter is not easily inferable from the former. In short, a description of used language is not the same as language being used.

from 'Uncovering grammar' by Scott Thornbury