Alexander derived his concept of `Asia' from the teaching of Aristotle, for whom `the inhabited earth' was surrounded by `the Great sea' Ocean, and was divided into three areas – `Europe, Libya and Asia.' Thus the earth was not round but flat, and `Asia' was limited on the west by the Tanais (Don), the inland sea and the Nile, and on the east by `India' and `the Great Sea' ... he was mistaken in supposing that from the ridge of the Paropamisadae (Hindu Kush) one would see `the outer sea' and that `India' was a small peninsula running east into that sea.