The article concerns Locke’s philosophy of language. After presenting Locke’s theory of meaning and his motivation for introducing it, the author summarises Locke’s taxonomy of signs and thereby shows that Locke is introducing a concept of the conventional sign as a symptom of belief (not as an icon for a thing or a state of things). On this basis, and on the basis of Locke’s division of the sciences, the article shows that the so-called doctrine of signs takes the place of metaphysics, i.e. of first philosophy. The author goes on to show, on the basis of a discussion of the words child and doctrine, that the aim of this doctrine is not purely theoretical, rather it is primarily educational: the doctrine itself is not well-supported by a theory that might serve as the grounding for other theories, instead it is above all a proposal for a new concept the concept of a sign which can aid the acquisition of knowledge.