ABSTRACT
Accounting for the emergence of novelty, of the genuinely new, is among the deepest mysteries facing students of development. Cognitive development consists, in part, of the acquisition of new representational resources, such as natural languages, written languages, mathematical and logical notations. Cognitive development also consists, in part, of the acquisition of new systems of concepts that allow the expression of thoughts previously unthinkable. This latter kind of novelty arises whenever knowledge acquisition involves conceptual change, and conceptual change concerns me here.
