In Patricia Curd's Pre-Socratic Reader, in the chapter on Parmenides, we have the following fragment from the Commentary on Aristotle's Physics by Simplicius:
It is right both to say and to think that is what-is: for it can be,
but nothing is not: these things I bid you ponder
For I [lacunae: back/begin for] you from this first route of enquiry
And then from that, on which mortals, knowing nothing,
Wander, two-headed: for helplessness in their
breasts steer their wandering mind. They are borne along
deaf and blind alike, dazed, hordes without judgement
for whom to be and not to be are thought to be the same
and not to be the same, and the path of all is backward-turning
Thus, (going from line 2, and using the word void for nothing); for Parmenides
void is not
And thus (in the monist interpretation) there is no causality and no change, but more precisely we might say that causality is not and that change is not.
After all, this coffee cup before me is, but neither is it experiencing change. So it has no change. But this is different from a non-existent coffee cup which by its very sense cannot experience change. So one might say change is not (by analogy to the expression of Parmenides); and again by analogy, that causality is not.
But he also argued that Being itself has no causality and no change.
Now, Hegel argued that Being and non-Being are equivalent, in a sense.
Now, if causality and change are not essences, we might venture that they are in a sense, essential properties.
We might venture also, if all essential properties are in common, then by analogy (if not by predicate) that they are the same; but not in the sense of identical.
Does this follow a standard interpretation of the opening of Hegel's Science of Logic where he states that:
Pure Being and Pure Nothing are therefore the same.