<p>Psychological essentialism is a well-established view within developmental psychology that has considerable philosophical significance. Recently it has come under pressure from both theoretical and experimental quarters. In this article my aim is to defend psychological essentialism against this assault. Doing this will involve placing psychological essentialism in the broader context of the theory theory approach to cognition which portrays humans as having a battery of distinct theories that have been developed to enable us to deal with a variegated external reality. Once this is recognised, data that initially seemed to pose problems for the psychological essentialist can be seen to be handled quite readily by them.</p>