ABSTRACT
Parmenides is responsible for the course taken by natural philosophy in the fifth century. No advance could be made without breaking through the network of his remorseless logic, which had left the world our senses show us with no basis in true being or reality. The essential weaknesses of his reasoning were not evident to his immediate successors; it remained for Plato to expose them. Meanwhile three attempts were made to evade some of his conclusions. If the sense world was to be rehabilitated as no mere illusion, it was necessary above all to justify the universal belief of mortals that plurality and change are facts which cannot be argued out of existence. Parmenides appeared to have proved that a manifold and changing world cannot be derived from a single homogeneous substance. His successors did not clearly see the ambiguities lurking in the terms ‘unity’ and ‘being’; but they saw that there was nothing irrational in the supposition of a plurality of real beings (https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315822945/7fd98c93-9fc7-4666-9464-f584df595414/content/fig3_1_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>), whether limited or illimitable in number, provided that these real beings were taken as ultimate. If cosmogony could no longer start from a single principle, it was still possible to build up a world-order starting from a plurality of ultimately real factors.
