All phenomena result from interactions between materials. Whatever happens in the world happens because things meet, influence one another, and produce change. This is the third foundational assumption.
An interaction occurs when one thing influences another while at the same time being included by it. Where influence means the ability to produce some change in others. The two participants are connected by the fact that one influences the other; in most interactions, both are influenced. There is no one-way action that leaves the other side untouched. To interact is to be mutually changed.
All behaviors are the result of an interaction between physical objects, whether natural or man-made. Wood burns in the presence of oxygen and a spark; salt dissolves when stirred into water; a metal cools when set in air. None of these happen without an interaction. The behavior we observe is, in every case, the visible signature of two or more things meeting and changing each other.
If phenomena were not the result of interactions, chemistry would have no story to tell. We could catalog materials and their features, and there it would end. Because phenomena are interactions, the catalog gives way to a dynamics: how materials behave when they meet, how the act of meeting transforms them, what new properties appear when one material is brought to another. The systemic approach is born here. Parts alone do not make a system; interactions do.
Question
Can something happen without an interaction?
Reveal Merrill's answer →Hide answer
No. Whatever happens, happens because materials meet and influence each other. Even what looks like a single thing in motion is the result of an interaction with the medium, the surface, or the previous state. The assumption is that the macroscopic world has no events without interaction.