Parmenides had argued that there were strict metaphysical requirements on any object of knowledge; the later Eleatics (named for following Parmenidean doctrines rather than for strictly geographical reasons), Zeno of Elea (born ca. 490) and Melissus of Samos (fl. ca. 440), extended and explored the consequences of his arguments. Zeno paid particular attention to the contrast between the requirements of logical argument and the evidence of the senses (Vlastos 1967 is a masterly treatment of Zeno;