In the late Platonic dialogue Parmenides, which places the youthful Socrates against one of the elders of Greek Philosophy - Parmenides; Parmenides says that the way to Philosophy is by the dialectic:
Socrates: But, then, what is to become of philosophy? Whither shall we turn, if the ideas are unknown?
to which Parmenides replies:
Yes, said Parmenides; and I think that this arises, Socrates, out of your attempting to define the beautiful, the just, the good, and the ideas generally, without sufficient previous training.
I noticed your deficiency, when I heard you talking here with your friend Aristoteles, the day before yesterday. The impulse that carries you towards philosophy is assuredly noble and divine; but there is an art which is called by the vulgar idle talking, and which is often imagined to be useless; in that you must train and exercise yourself, now that you are young, or truth will elude your grasp.
Socrates asks the obvious question:
And what is the nature of this exercise, Parmenides, which you would recommend?
to which he replies:
That which you heard Zeno practising...but I think that you should go a step further, and consider not only the consequences which flow from a given hypothesis, but also the consequences which flow from denying the hypothesis; and that will be still better training for you.
Hegel of course famously developed the notion of:thesis/anti-thesis and sublation to a synthesis; which one can, it appears, discern this in Parmenides; or a hint of it.
Is this correct? Does anyone else, before Hegel, press this notion of the dialectic through in this manner?