A Realistic Theory of Categories: An Essay on Ontology

The book is an original treatise designed to defend an original, non-Aristotelian theory of categories. Chisholm argues that there are necessary things and contingent things; necessary things being things that are not capable of coming into being or passing away. He defends the argument from design, and thus includes the category of necessary substance (God). Further contentions of the essay are that attributes are also necessary beings, but not necessary substances, and that human beings are contingent substances but may not be material substances.