The idea that grammar can be justified by reference to reality in the sense in which an empirical proposition is justified by reference to what makes it true is incoherent. The rules for the use of names, e.g. 'red', do not mirror the metaphysical nature of the colour, but constitute it. Grammatical propositions', e.g. 'Nothing can be red and green all over', are in effect rules, not descriptions of reality. What appear to be metaphysical necessities are in effect no more than the shadows cast upon the world by our methods of representation, our rules for the use of expressions. Concepts are not 'correct', let alone justifiable as true, but only more or less useful for our purposes.
Alternative grammars are conceivable.
Themes in the Philosophy of Wittgenstein , rev. The Oxford Companion to Philosophy 2. The Oxford Companion to Philosophy 4. All rights reserved.