Acquisition of sentient-nonsentient distinction in 48 children between four- and seven-years-of-age occurred later than animate-inanimate distinction. The children's use of naturalistic or nonnaturalistic explanations depended on the logical nature of events in which objects were involved rather than familiarity with objects themselves. Ability to provide naturalistic explanations of physical phenomena may be related to children's acquisition of sentient-nonsentinent distinction. (Author/RH)