I propose a theory of conceptual development in which concept possession consists in seeing the world aright. The capacity to see things aright is primitive; it is not explained in terms of grasp of a theory or in terms of assimilation of socially determined norms of word use. The educational task in promoting conceptual development is to train the forms of awareness by which the learner comes to see the world correctly. I sketch the consequences of this approach for understanding expertise by drawing upon ideas that inform an ongoing research project investigating the attention-dependent knowledge bases of experienced classroom teachers. One of the distinctive features of the theory is the central role it gives the concept of judgement in the account of concept possession so that conceptual development is theorised as an apprenticeship in judgement.