Reductionism, holism, causality, and entropy

Reductionism is the idea according to which a complex system can be analyzed by decomposing it into smaller and simpler entities. For instance, the complex properties of macroscopic systems can often be understood from the simpler laws that govern the atoms and molecules they are made of. The opposite idea is holism, according to which the properties of an entity are best understood in the context of the larger system it is part of. Somehow, the theory of evolution, in which the morphology of individuals is shaped by their environment, is a holistic one.

The fact that the two approaches (reductionism and holism) can both be used to define a causality relation is puzzling. When passing from holism to reductionism, one almost switches the cause and the effect. When two facts are related by some logical link, which one is to be considered as the cause? And which one is the effect? It seems to me that we always chose the simplest fact as the cause. In order words, it is easy for us to understand that simple causes can have complex effects, but we generally do not accept the other possibility. I would be most happy to discuss this with anyone!

Causality is obviously related to the notion of time. The cause always comes before the effect, and this is basically how the direction of time is defined. Now, if we really tend to chose the simplest facts to be the cause of complex effects, we tend to bias the direction of time towards an increasing complexity. Isn’t that oddly related to the impossibility of decreasing the entropy of an isolated system, as time increases?