Reciprocity (n.) is only causality itself: the cause not only has an effect, but in the effect it relates to itself as cause.
Reciprocity (n.) bends the straight line of causes and effects back into a circle — and in all those unthinking repetitions there is only one relation.
Reciprocity (n.) is representative of a logical superiority that makes it more suitable for the understanding of higher, biological and social phenomena than is unidirectional causality.
Reciprocity (n.) stands on the threshold of the Concept — which is exactly why stopping there is unconceptual: saying Spartan customs cause the constitution and vice versa comprehends neither.
Reciprocity (n.) is the completion of the division of actuality which proves to be the notion. It is the grasping of the thing at the point where cause/effect, action/reaction/ possibility/necessity have completely merged with one another. It is sometimes called 'interaction'.