 Like Hawley and Bird, E. J. Lowe takes natural kinds to be entities (1998, 2006a, 2006b). Thus Lowe is a natural kind realist. Furthermore, he takes natural kinds—substantial universals in his terminology—to constitute an irreducible ontological category (one category in his four-category ontology). Hence he is a natural kind fundamentalist. Lowe argues that recognizing the ontologically fundamental distinction between substantial universals (natural kinds) and non-substantial universals (properties) accounts for the laws of nature in a manner that, while avoiding the problems of a regularity account, may nonetheless do without Armstrong’s second order relation of necessitation, itself a relational universal (Armstrong 1983, 75–110). Consider the law that planets travel in ellipses. According to Lowe’s account, this should be understood as a matter of the kind planet being characterized by the property travels in an ellipse. (One might query whether all laws can be given this form and so whether the fact that some general truth is a law should be explained this way. For what makes planets travel in ellipses is the fact that they have mass and hence little to do with their being planets. For example, Kepler’s law is an application of Newton’s laws, but the latter concerns quantities (mass, distance), which should be understood as universals not kinds.)