Abstract
Kant's teleological principle is a regulative, not a constitutive, principle of reason, ordering but not creating the understanding's concepts of objects. The principle is both heuristic for suggesting explanations in terms of efficient causality and a reminder of such explanations' insufficiency. But Kant states the rough content as well as the existence of an historical pattern. Reason and understanding and philosophy and science are analogously related. Since historians disagree over which, if any, principles are used in explanations, reason, represented by philosophers, intrudes so on history. Further, the falsifiability of any attempted applications leaves the teleological principle itself untouched.