An interaction is composed of transitive actions. Now transitive actions can be analyzed in two ways: first, into intransitive actions, e.g. if the hand pushed a box, then both the box and the hand moved; and if the line reeled in the fish, then the line retracted and the fish rose. Leave this sort of analysis aside. Interaction can also be analyzed into distinct transitive actions: reeling in the fish means both that the line acts on the fish and the fish acts on the line. This last sense is the reality captured by Newton’s third law, where every action (read transitive action) is only a part of a larger interaction, and so, for the physicist, every action of one thing on another is an interaction.
A transitive action is to an interaction as one to many. But all physical transitive actions are interactions, and so any physical action is a multitude. The individual transitive actions are only potential parts. To analyze a physical action into an actual transitive action requires analyzing the cause to a non-physical source. This analysis is not into the potential parts of the interaction (potential parts are not actual), but it is nevertheless the analysis of a physical action as physical. Considered in this sense, all physical action is analyzed into a way of taking part in the transcendent unity of a non-physical cause.