Coming to later centuries, we find indications that the Neo-Platonist philosophy may have been influenced by the Sankhya system, which flourished in the first centuries of our era, and could easily have become known at Alexandria owing to the lively intercourse between that city and India at the time. From this source Plotinus (204-269 A.D.), chief of the Neo-Platonists, may have derived his doctrine that soul is free from suffering, which belongs only to matter, his identification of soul with light, and his illustrative use of the mirror, in which the reflections of objects appear, for the purpose of explaining the phenomena of consciousness. The influence of the Yoga system on Plotinus is suggested by his requirement that man should renounce the world of sense and strive after truth by contemplation. Connection with Sankhya ideas is still more likely in the case of Plotinus's most eminent pupil, Porphyry (232-304 A.D.), who lays particular stress on the difference between soul and matter, on the omnipresence of soul when freed from the bonds of matter, and on the doctrine that the world has no beginning. It is also noteworthy that he rejects sacrifice and prohibits the killing of animals. The influence of Indian philosophy on Christian Gnosticism in the second and third centuries seems at any rate undoubted. The Gnostic doctrine of the opposition between soul and matter, of the personal existence of intellect, will, and so forth, the identification of soul and light, are derived from the Sankhya system. The division, peculiar to several Gnostics, of men into the three classes of pneumatikoi, psychikoi, and hylikoi, is also based on the Sankhya doctrine of the three gunas. Again, Bardesanes, a Gnostic of the Syrian school, who obtained information about India from Indian philosophers, assumed the existence of a subtle ethereal body which is identical with the linga-çarira of the Sankhya system. Finally, the many heavens of the Gnostics are evidently derived from the fantastic cosmogony of later Buddhism. With regard to the present century, the influence of Indian thought on the pessimistic philosophy of Schopenhauer and Von Hartmann is well known. How great an impression the Upanishads produced on the former, even in a second-hand Latin translation, may be inferred from his writing that they were his consolation in life and would be so in death.