I'll say you picked a good one if you are starting out on "non-Koine" Greek!
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Not only intense philosophy, but dactylic hexameter to boot.
ἡ µὲν ὅπως ἔστιν τε καὶ ὡς οὐκ ἔστι µὴ εἶναι...
Notice how ἔστι is accented in both instances. The first is the existential use, the second followed by the infinitive renders possibility, something like that the first way is existence and that it is not possible not to exist...
If you have watched the 4th original Trek movie, "The Voyage Home," this is actually paraphrased when Spock is relearning everything before the computer, something to the effect of "nothing unreal has existence."
Here is the Stanford introduction to Parmenides:
Parmenides of Elea, active in the earlier part of the 5th c. BCE, authored a difficult metaphysical poem that has earned him a reputation as early Greek philosophy’s most profound and challenging thinker. His philosophical stance has typically been understood as at once extremely paradoxical and yet crucial for the broader development of Greek natural philosophy and metaphysics. He has been seen as a metaphysical monist (of one stripe or another) who so challenged the naïve cosmological theories of his predecessors that his major successors among the Presocratics were all driven to develop more sophisticated physical theories in response to his arguments. The difficulties involved in the interpretation of his poem have resulted in disagreement about many fundamental questions concerning his philosophical views, such as: whether he actually was a monist and, if so, what kind of monist he was; whether his system reflects a critical attitude toward earlier thinkers such as the Milesians, Pythagoreans, and Heraclitus, or whether he was motivated simply by more strictly logical concerns, such as the paradox of negative existentials that Bertrand Russell detected at the heart of his thought; whether he considered the world of our everyday awareness, with its vast population of entities changing and affecting one another in all manner of ways, to be simply an illusion, and thus whether the lengthy cosmological portion of his poem represented a genuine attempt to understand this world at all.
https://plato.stanford.edu/entries/parmenides/