The purpose of this thesis is to examine the fundamental aspects of Suarez's doctrine of being. Specifically, these aspects include: his concept of being and the manner in which he develops his definition of being as 'essence and existence'. This thesis attempts to illustrate the Suarezian position on, and elucidate the distinction he draws between, essence and existence. Further, this thesis demonstrates that his position was the unavoidable result of Suarez's first premise on the nature of being in general. This result is significant with regard to the modification of Aquinas' view and the regnant Thomistic position.