The authors examine recent theoretical perspectives of the development of the animate-inanimate distinction in infancy. From these theoretical views emerge 7 characteristic properties, each related to physical or psychological causality, that distinguish animates from inanimates. The literature is reviewed for evidence of infants' ability to perceive and understand each of these properties. Infants associate some animate properties with people by 6 months, but they do not associate the appropriate properties to the broad category of animates and inanimates until at least the middle of the 2nd year. The authors offer a theoretical proposal whereby infants acquire knowledge about the properties of different object kinds through a sensitive perceptual system and a domain general associative learning mechanism that extracts correlations among dynamic and static features.