Suppose that we ruled out all but one possible explanations for a phenomenon. The remaining explanation H is the poorest and most contrived explanation you can imagine. But a poor and contrived explanation is still an explanation. And in this case it is the best explanation by a mile: none
other comes close, as all others have been ruled out. Thus by Inference to Best Explanation:
- We should accept H.
- If there was any chance that there simply was no explanation, the hypothesis that there is no explanation would be preferable to H, given how poor and contrived H is.
- So, there is no chance that there is simply is no explanation.