Heraclitus discovered that the concept of unity of opposites applies to the inner human psyche as well as the natural world. "The great cosmic cycle is only the ordinary cycle of natural change and human life writ large." ( page 136) Heraclitus' understood "human life and death as a unity, which forms the central insight in what Heraclitus means by 'wisdom'." (page 110) Kahn argues that Heraclitus view is "congenial to Hegel" with its positive interpretation of negativity--recognizing the life enhancing function of the negative term. Heraclitus recognized that "all things come to pass in accordance with conflict." (page 205)
According to Kahn, "The gods of Heraclitus, . . .can only be the elemental powers and constituents of the cosmos, from which our life comes and to which it returns." This view conflicted with the general religion of the day and with philosophical successors such as Socrates, Plato, and Aristotle who believed that celestial objects were divinities, not material objects.
Heraclitus' views also conflicted with his contemporary Parmenides who argued that nature was an "unchanging constancy." (The Presocratic Tradition from Parmenides to Democritus, WKC Guthrie, Cambridge University Press, 1965). Ironically, a pupil of Parmenides, Zeno of Elea, coined the word 'dialectics' to describe a means of argumentation using paradoxes to prove Parmenides point about reality being unchanging, motionless and indivisible. Similarly Plato used the term dialectic to refer to his world view as developed through questions and answers aimed at showing absurdities in opposing views. Aristotle used the term more as a description of the technique than as a world view itself. So the actual Greek usage of the term dialectic was more limited than today's term, and in some ways was directly opposed to the current usage.
It wasn't until Hegel that dialectic came to mean a broader philosophical world view. The Encyclopaedia Brittanica, Macropedia Vol 4, 15th Edition, 2005, sums it up under the heading "Dialectics"--"originally a form of logical argumentation, but now a philosophical concept of evolution applied to diverse fields including thought, nature, and history."