Parmenides seems to fasten on that which is one in formula, Melissus on that which is one in matter, for which reason the former says that it is limited, the latter that it is unlimited; while Xenophanes, the first of this school of monists (for Parmenides is said to have been his pupil), gave no clear statement, nor does he seem to have grasped either of these two kinds of unity, but he contemplates the Some authorities read: 'For Alcmaeon lived during the old age of Pythagoras, and he expressed himself. .'.