Parmenides of Elea, a revolutionary and enigmatic Greek philosophical poet, was the earliest defender of Eleatic metaphysics. He argued for the essential homogeneity and changelessness of being, rejecting as spurious the world’s apparent variation over space and time. His one poem, whose first half largely survives, opens with the allegory of an intellectual journey by which Parmenides has succeeded in standing back from the empirical world. He learns, from the mouth of an unnamed goddess, a dramatically new perspective on being. The goddess’s disquisition, which fills the remainder of the poem, is divided into two parts; the Way of Truth and the Way of Seeming.
The Way of Truth is the earliest known passage of sustained argument in Western philosophy. First a purportedly exhaustive choice is offered between two ‘paths’ – that of being, and that of not-being. Next the not-being path is closed off: the predicate expression ‘… is not’ could never be supplied with a subject, since only that-which-is can be spoken of and thought of. Nor, on pain of self-contradiction, can a third path be entertained, one which would conflate being with not-being – despite the fact that just such a path is implicit in the ordinary human acceptance of an empirical world bearing a variety of shifting predicates. All references, open or covert, to not-being must be outlawed. Only ‘… is’ (or perhaps ‘… is…’) can be coherently said of anything.
The next move is to seek the characteristics of that-which-is. The total exclusion of not-being leaves us with something radically unlike the empirical world. It must lack generation, destruction, change, distinct parts, movement and an asymmetric shape, all of which would require some not-being to occur. That-which-is must, in short, be a changeless and undifferentiated sphere.
In the second part of the poem the goddess offers a cosmology – a physical explanation of the very world which the first half of the poem has banished as incoherent. This is based on a pair of ultimate principles or elements, the one light and fiery, the other heavy and dark. It is presented as conveying the ‘opinions of mortals’. It is deceitful, but the goddess nevertheless recommends learning it, ‘so that no opinion of mortals may outstrip you’.
The motive for the radical split between the two halves of the poem has been much debated in modern times. In antiquity the Way of Truth was taken by some as a challenge to the notion of change, which physics must answer, by others as the statement of a profound metaphysical truth, while the Way of Seeming was widely treated as in some sense Parmenides’ own bona fide physical system.