Unity of opposites

The unity of opposites (Latin; unio oppositorum) is the central category of dialectics, said to be related to the notion of non-duality in a deep sense. It defines a situation in which the existence or identity of a thing (or situation) depends on the co-existence of at least two conditions which are opposite to each other, yet dependent on each other and presupposing each other, within a field of tension. The unity of opposites was first suggested to the western view by Heraclitus (c. 535 – c. 475 BC), a pre-Socratic Greek thinker. Philosophers had for some time been contemplating the notion of opposites. Anaximander posited that every element had an opposite, or was connected to an opposite (water is cold, fire is hot). Thus, the material world was said to be composed of an infinite, boundless apeiron from which arose the elements (earth, air, fire, water) and pairs of opposites (hot/cold, wet/dry). There was, according to Anaximander, a continual war of opposites Anaximenes of Miletus, a student and successor of Anaximander, replaced this infinite, boundless arche with air, a known element with neutral properties. According to Anaximenes, there was not so much a war of opposites, as a continuum of change. Heraclitus, however, did not accept the Milesian monism and replaced their underlying material arche with a single, divine law of the universe, which he called Logos. The universe of Heraclitus is in constant change, while remaining the same. That is to say, when an object moves from point A to point B, a change is created, while the underlying law remains the same. Thus, a unity of opposites is present in the universe simultaneously containing difference and sameness. An aphorism of Heraclitus illustrates the idea as follows: The road up and the road down are the same thing. (Hippolytus, Refutations 9.10.3) This is an example of a compresent unity of opposites. For, at the same time, this slanted road has the opposite qualities of ascent and descent.