Parmenides  (trans. Richard McKirahan, Philosophy before Socrates)

2. Come now, I will tell you – and bring away my story safely when you have heard it-
the only ways of inquiry there are to think:
the one, that it is and that it is not possible for it not to be,
is the path of Persuasion (for it attends upon the Truth),
the other, that it is not and that it is necessary for it not to be,
this I point out to you to be a path completely unlearnable,
for neither may you know that which is not (for it is not to be accomplished)
nor may you declare it.

3. For the same thing is [or, is there] for thinking and for being. [or, For thinking and being are the same].

4. But gaze upon things which although absent are securely present in thought.
For you will not cut off what is from clinging to what is,
neither being scattered everywhere in every way throughout the kosmos
nor being brought together.

5. For me, where I am to begin from is the same [literally, common]
for to there I will come back again.

6. That which is there to be spoken and thought of must be.
For it is possible for it to be,
but not possible for nothing to be.  I bid you consider this.
For I bar your way from this first way of inquiry,
but next from the way on which mortals, knowing nothing,
two-headed, wander. For helplessness
in their breasts guides their wandering mind.  But they are carried on
equally deaf and blind, amazed, hordes without judgment,
for whom both to be and not to be are judged the same and
not the same, and the path of all is backward-turning.

7.  For in no way may this prevail, that things that are not, are.
But you, bar your thought from this way of inquiry,
and do not let habit born from much experience compel you along this way
to direct your sightless eye and sounding ear and tongue,
but judge by reason the heavily contested refutation
spoken by me.

8. There is still left a single story
of a way, that it is.  On this way there are signs
exceedingly many – that being ungenerated it is also imperishable,
whole and of a single kind and unshaken and complete.
Nor was it ever nor will it be, since it is now, all together,
one, continuous.  For what birth will you seek for it?
How and from where did it grow?  It will not permit you to say
or to think <that it grew> from what is not; for it is not to be said or thought
that it is not.  What necessity would have stirred it up
to grow later rather than earlier, beginning from nothing?
Thus it must either fully be or not.
Nor will the force of conviction ever permit anything to come to be
from what is not, besides it [i.e. besides what is not].  For this reason, Justice has permitted it [i.e. what is]
neither to come to be nor to perish, relaxing her shackles,
but holds it fast.  But the decision about these matters lies in this:
it is or it is not.  But it has been decided, as is necessary,
to let go the one way as unthinkable and nameless (for it is not
a true way) and that the other is and is real.
How could what is be in the future?  How could it come to be?
For if it came into being, it is not, nor <is it> if it is ever going to be.
In this way, coming to be has been extinguished and destruction is unheard of.
Nor is it divided, since it all is alike;
nor is it any more in any way, which would keep it from holding together,
or any less, but it is all full of what is.
Therefore, it is all continuous, for what is draws near to what is.
But unchanging in the limits of great bonds,
it is, without start or finish, since coming to be and destruction
were banished far away and true conviction drove them off.
Remaining the same in the same and by itself it lies
and so stays there fixed; for mighty Necessity
holds it in the bonds of a limit, which pens it in all round,
since it is right for what is to be not incomplete;
for it is not lacking; if it were <lacking>, it would lack everything.
Thinking and the thought that it is are the same.
For not without what is, in which it is expressed,
will you find thinking; for nothing else either is or will be
except that which is, since Fate shackled it
to be whole and unchanging; wherefore it has been named all names
mortals have established, persuaded that they are true –
to come to be and to perish, to be and not <to be>,
and to change place and alter bright color.
But since there is a further limit, it is complete
on all sides, like the bulk of a well-rounded ball,
evenly balanced in every way from the middle; for it must be not at all greater
or smaller here than there.
For neither <is it the case that> what is not is – which would stop it from reaching
its like – nor <is it the case that> what is is in such a way that there could be more of what is
here and less there, since it is all inviolate;
for equal to itself to all sides, it meets with its limits uniformly.