Three experiments with a methodology called inductive categorization examined 12-16-, and 20-month-olds' categorization of animals and vehicles with and without functional parts as well as their inductive inferences about the motion properties of the objects in these classes. The experiments showed that infants at 12 months use object parts to categorize after a brief learning period, infants at 16 months attend spontaneously to object parts to categorize, and infants at 20 months use object parts and other features to categorize. The experiments also revealed that 12-month-olds have little knowledge about the motion properties of objects, 16-month-olds have associated specific object parts with those properties, and 20-month-olds have generalized from object parts to other features. Taken together, these experiments provide support for the domain-general approach to early concept development, and they are the first to show a relationship between inductive inference and categorization in infancy.