Parmenides, answered from the texts and cited to the page.
The goddess announced two routes, and only two that reason can conceive.1 The first: that a thing is, and that it is not possible for it not to be — this is the journey of persuasion, for persuasion attends on reality.2 The second: that a thing is not, and that it must needs not be — this I tell you is a path wholly without report, for you can neither know what is not, since that is impossible, nor tell of it.3
Why impossible? Because the same thing is for conceiving as is for being.4 What has no being cannot be known, cannot be named, cannot even serve as the starting-point of an inquiry — the formula is not turns out not to name a genuine way at all, but only the prima facie appearance of one, which collapses the moment you try to follow it.5 Yet mortals walk neither route cleanly.
They stray two-headed, by whom this has been accepted as both being and not being the same and not the same, and for all of whom their journey turns backwards again.6 Bewilderment in their own breasts directs their mind astray; they are borne on deaf and blind alike, without judgement.7 This is the third condition — not a genuine route of inquiry but the wandering that results when the founding distinction between is and is not is blurred.
What remains, then, when both the impossible route and the mortal wandering are refused? Only one story of the way is still left: that a thing is.8 From that single premise the goddess draws the signs of what genuinely is — ungenerated, imperishable, whole, immovable, complete — by deduction, each sign following from the impossibility of mixing being with not-being.
That deductive unfolding, from the route-formula through the signs, is what I call Aletheia, the well-rounded heart of truth.9 The poem does not end there. The goddess promises that I will learn both the unshaken heart of truth and the opinions of mortals, in which there is no true conviction — so that no judgement of mortals will ever outstrip me.10
That second teaching, the Doxa, is the cosmology mortal cognition produces once it has named two contraries and treated one of them as standing apart from what is. It is mine; it is also the disclosure of where mortal speech inevitably goes. Both things at once.
Come now, I will tell you (and do you preserve my story, when you have heard it) about those ways of enquiry which are alone conceivable.The Fragments of Parmenides, pp. 55–57
The one, that a thing is, and that it is not for not being, is the journey of persuasion, for persuasion attends on reality.The Fragments of Parmenides, pp. 55–57
the other, that a thing is not, and that it must needs not be, this I tell you is a path wholly without report, for you can neither know what is not (for it is impossible) nor tell of it.The Fragments of Parmenides, pp. 55–57
for the same thing is for conceiving as is for being.The Fragments of Parmenides, pp. 57–59
The formula οὐκ ἔστιν turns out not to be the name of a 'real way' of enquiry, because, as P. at once observes, a subject which is not (anything), i.e. has no being, cannot be known.The Fragments of Parmenides, pp. 293–294
by whom this has been accepted as both being and not being the same and not the same, and for all of whom their journey turns backwards again.The Fragments of Parmenides, pp. 57–59
for perplexity in their own breasts directs their mind astray and they are borne on deaf and blind alike in bewilderment, people without judgement.The Fragments of Parmenides, pp. 57–59
The only story of the way still left is that a thing is.The Fragments of Parmenides, pp. 288–289
Fragments 3, 4, 5, 6, 7 form a recognisably continuous argument... 'I shall tell you—and preserve my story carefully—about the only ways of enquiry which reason can conceive.'The Fragments of Parmenides, pp. 288–289
ἠμὲν ἀληθείης εὐπειθέος ἀτρεμὲς ἦτορ / ἠδὲ βροτῶν δόξας, τῇς οὐκ ἔνι πίστις ἀληθής" ["the unshaken heart of well-rounded truth and the opinions of mortals, in which there is no true conviction."]The Fragments of Parmenides, pp. 55–57