Edith Stein's work revolves around one central question, namely, the identity of the person. Discussions of this topic are already present in Stein's dissertation. I examine her theory of identity, developed throughout her work and maturing in her magnum opus, Finite and Eternal Being, in three stages, each of which is historically relevant and original. First, Stein's development of the question is examined phenomenologically, focusing on Stein's early work. Second, I will show how Stein takes her early phenomenological positions concerning the nature of the human person and combines them with Greek and medieval insights into ontology. Here I focus on Finite and Eternal Being. Finally, I concentrate on the meaning and value of Stein's theory of identity as it contributes to a theory of the person in connection with Greek and medieval metaphysics, and a phenomenological philosophy of consciousness. Together, the three stages of the essay will demonstrate Stein's systematic contribution toward a theory of personal identity, one of the most difficult problems of philosophy.