This is the theory that, when there are multiple possible explanations of an event or phenomenon, the simplest is the best. Psychological egoism Inductive generalization Descartes's dilemma Occam's razor

The theory which states that when there are multiple possible explanatons of an event or a phenomenon, the simplest is the best would be Occam's razor.

However, it's important to note that this idea actually states that we shouldn't necessarily multiply ontological entities, which doesn't really mean the easiest solution necessarily.