Locke's Essay Concerning Human Understanding treats words as outward marks of inner ideas. That position seems to imply that language is private. Wittgenstein's private language argument in the Philosophical Investigations challenges the implication at its root. This paper looks at the tension inside Locke's theory of meaning and at Cook's reading of Wittgenstein, with recent scholarship in view. Locke's ideational theory faces a structural conflict. It holds that thought is unknowable, and it also holds that words express ideas. Wittgenstein's treatment of private language is better understood as a grammatical investigation than as a single argument. Its aim is to dissolve the temptation to treat sensations as private objects. Ying Li's recent work (2024) shows that Locke is not the private-language theorist he is often taken to be: the meaning of words is settled by public use. Recent research tends to read the private language argument as a grammatical therapy for the urge to privatize thought, not as an empirical thesis about language.