The purpose of this thesis Is to trace the history of the Ideas of the soul and immortality In Greek thought, and their adoption and comprehension by M. Tullius Cicero In his essays De Senectute, Tusculanae Dlsputationes, an Somnium Sciplonis. Special emphasis is placed upon Plato’s Socratic Dialogues which were a summary of the various beliefs and arguments of the fifth and fourth centuries B.C. and which served as major sources for Cicero’s philosophical essays treating the soul. The second most significant school of thought which had an influence upon Cicero was the Stoa. These two philosophies, one Idealistic, the other materialistic, contended for the primacy in the private thinking of the renowned Roman author whose eclectical mind was well suited for selecting the ideas of different philosophical systems and combining them into a whole. The fluctuation of his thinking bears the mark of the scepticism of his age which had a basic attitude of mistrust of convictions. This mistrust is perceivable In his hesitation to give an unconditional assent to the belief In Immortality, although he Is very close to accepting it.