The Reach of an Explanation

The reach of an explanation is not a principle of induction It is not something that the creator of the explanation can use to obtain or justify it. We find out about it only after we have the explanation sometimes long after. There's nothing here I'm afraid to bolt about hard to vary so no rather than Minger on this any longer. The answer to the question your question is why is the reach of a good explanation determined by how hard it is to be by how hard to vary it is Is it isn't?