Hegel: Shorter Logic/Essence/Actuality/Reciprocity
The characteristics which in Reciprocal Action are retained as distinct are [a] potentially the same. The one side is a cause, is primary, active, passive, etc., just as the other is. Similarly the presupposition of another side and the action upon it, the immediate primariness and the dependence produced by the alternation, are one and the same on both sides. The cause assumed to be first is on account of its immediacy passive, a dependent being, and an effect. The distinction of the causes spoken of as two is accordingly void: and properly speaking there is only one cause, which, while it suspends itself (as substance) in its effect, also rises in this operation only to independent existence as a cause.
But this unity of the double cause is also [b] actual. All this alternation is properly the cause in act of constituting itself and in such constitution lies its being. The nullity of the distinctions is not only potential, or a reflection of ours (§155). Reciprocal action just means that each characteristic we impose is also to be suspended and inverted into its opposite, and that in this way the essential nullity of the ‘moments’ is explicitly stated. An effect is introduced into the primariness; in other words, the primariness is abolished: the action of a cause becomes reaction and so on.