***Natural explanations are the only thing that are testable.***
Very true.
What you can’t test is that there is a natural explanation for everything. That is simply not knowable and in fact flies in the face (in some instances) of natural law.
A few examples:
1. The Law of the Conservation of Matter states (my own words) that by natural processes, matter can neither be created or destroyed, although it can change form. That begs the question: If it can’t be created or destroyed by natural processes, where did it come from? It must have been ordained from outside of nature (Supernaturally).
2. The Law of Cause and Effect (Causality) says that for every effect there must be a pre-existent cause that is greater than the effect. Since you can’t have an infinite number of causes (in a universe that had a beginning) the first cause must have come from outside of nature (again Supernaturally).
I can give you other examples but I think I’ll just rest on those two.
God of the gaps fallacy.
“where did it come from? It must have been ordained from outside of nature (Supernaturally).”
Maybe a better answer is that we don’t know yet.
Over time people have thought just about everything that wasn’t obvious was supernatural. The lost is almost endless (rain, heat, drought, disease, tornadoes, lightning, earthquakes, landslides, eclipses, the moon, comets etc, etc). Thanks to the efforts of science we now have reasonable, non-supernatural answers to an enormous percentage of those things. What makes you think we won’t eventually get some answers to the things that remain?