Let's say we have 16 distinct phenomena. All of them are currently explained by a rooted tree T of explanations of depth 4. Say, we come across 8 new phenomena.

Let's say we have 16 distinct phenomena. All of them are currently explained by a rooted tree T of explanations of depth 4. Say, we come across 8 new phenomena. Suddenly you can't rejig or shake your tree T anyhow. You have to preserve the original structure of T or at least relationships while constructing a new tree R such that it not only explains old 16 phenomena but also the new 8 as well. We might construct a new tree R such that tree T is a subtree of it. This new tree covers more ground and has more depth. In this sense, new explanations are constrained by whatever that came before and they are tasked with explaining more on top of that. There are very few ways to do it. In physics, they call the more general law to be valid at all time scales, energy scales and length scales, velocity scales and so on.