 While Zeno and Melissus reinforced Parmenides’ distinction between what-is (i.e., what must be) and what appears, other post-Parmenidean thinkers accepted Parmenides’ arguments against coming-to-be and passing-away (as characterizing what-is), and about the stable nature of what is ultimately real, and argued that these arguments did not rule out the possibility of metaphysically-based (or rational) cosmology. Both Anaxagoras and Empedocles worked within the Parmenidean pattern while developing distinct cosmological systems that addressed their own particular concerns (especially in the case of Empedocles, concerns about the proper way to live). 