Abstract
Three Dimensionalists and Four Dimensionalists are engaged in a debate on the topics of persistence and mereology. In this paper, I explore implications of Four Dimensionalism for the formulation of the criterion of personhood and on the question of which individuals satisfy that criterion. In my discussion I argue that the Four Dimensionalist has reason to identify a human person with a proper part of a human organism, and that the Four Dimensionalist has reason to believe that if there is something morally wrong with human abortion or infanticide, it cannot be grounded in claims about the moral status of persons