This paper explores the arguments against the compatibility of classical metaphysics (Aristotelian-Thomistic) and theistic evolution. It begins with presenting the line of division between theists and atheistic evolutionists regarding the origin of the universe. Next, it moves to definitions of the terms evolution and species. The core of the paper consists of the five reasons why theistic evolution is excluded by Thomistic metaphysics. Among these are the problem of sufficient cause, accidental changes generating substantial changes, the reduction of causality in theistic evolution and the problem of the order in the universe. This is followed by a presentation of the positive teaching of Aquinas on the origin of species. Finally, the article responds to the three common arguments put forward by theistic evolutionists who seek to either accommodate or dismiss classical metaphysics.