Abstract: In a full explanation, the explaining factors necessitate the phenomena to be explained. A special kind of full explanation is a complete explanation, one where none of the explaining factors can themselves be explained by factors operating at the time in question. A special kind of complete explanation is an ultimate explanation, one in which one of the explaining factors has any explanation at all by further factors, and the explaining factors constitute the ultimate brute facts. A special kind of ultimate explanation is one where the explaining factors are either self-explanatory or logically necessary. There can be no absolute explanations of contingent phenomena. Our grounds for believing that we have reached a complete or ultimate explanation is that we have reached a probably true explanation, and that there is a good reason to suppose that there is no probably true explanation of it.

Keywords: absolute explanation, Aquinas, complete explanation, Duns Scotus, full explanation, explanation, probability, ultimate explanation,