  How would one go about establishing via a purely deductive argument that a deer’s suffering a slow and painful death because of a forest fire, or a child’s undergo lingering suffering and eventual death due to cancer, is not logically necessary either to achieve a greater good or to avoid a greater evil?  If one had knowledge of the totality of morally relevant properties, then it might well be possible to show both that there are no greater evils that can be avoided only at the cost of the evil in question, and that there are no greater goods that are possible only given that evil.  Do we have such knowledge?  Some moral theorists would claim that we do, and that it is possible to set out a complete and correct moral theory. But this is certainly a highly controversial metaethical claim, and, as a consequence, the prospects for establishing a premise such as (1) via a deductive argument do not appear promising, at least given the present state of moral theory.