To which you replied:
The third proposition does not neccesarily or logically follow from the first two... Presumably, you do not deny that it is possible that the actions of an unobservable agent could have empirical consequences in the present, do you?
Cordial sophistry.
Assuming without justification that that the only scientifically acceptable causes in science are mechanistic (as to opposed to the actions of intelligent agency) is the sophistry. If the same methodological criteria were applied impartially to evolutionary theory then it doesn't meet the strict criterion of testability and positive verification by repeated observation of cause-effect relationships either. There are a host of Darwinian theoretical postulations of past, unobserved and unobservable events that purport to account for present impirical biological data. In either case the "testabilty" lies in the putative explanatory power rather than verification by direct and repeated observation. In the case of a theoretical postulate of ID, the past action of an unobservable agent could have empirical consequences in the present just as an unobservable genealogical relationship between organisms does.
Cordially,