  Recent psychological research on concept formation has suggested that children do not generally form concepts by learning necessary and sufficient conditions for their application, but rather by coming to use prototypical examples as reference guides. Thus a robin (rather, of course, than a penguin) might be the child’s prototype for ‘bird’. The child, like the adult, might then be credited with having the concept, bird, without the child’s ever being able to specify, successfully, necessary and sufficient conditions for something to count as a bird. This finding seems to have implications for the proper role and importance of conceptual analysis in philosophy. It is also a case in which we should let what we come to know about cognitive development in children help shape our epistemology, rather than counting on our antecedently formulated epistemology to shape our conception of cognitive development in children (see Rosch and Lloyd, 1978, and Gelman, 2003).