This course will provide an introduction to the study of Being in its most universal aspects. The structure and principles of Being, the First Cause, will be investigated. The course will also examine Being as present in the multiplicity of finite beings encountered in everyday experience. The notions of act and potency, the doctrine of participation, and the doctrine of composition of essence with act of Being will be explored. While the predominant emphasis of the course will be on the metaphysics of Saint Thomas Aquinas, consideration will also be given to the most important philosophers of metaphysics from ancient Greece to the present.