A short thought: I think that efficient causes are sometimes misunderstood by modern thinkers to be identified with the kind of causation which early modern thinkers bequeathed to us, though they got rid of Aristotle’s other three kinds (Formal, Material, and Teleological). However, the proper definition of efficient causes is wider than the notion of physical causation employed in the early modern period. For instance, efficient causes need not precede their effects in time; they may be simultaneous with them, or indeed they may be after their effects (those who subscribe to two-way causation think there may be such causes whose ’cause’ is in the future relative to its ‘effects’), or again they may be completely non-temporal. Even if these aren’t so of Aristotle’s philosophy, they are so of his category.
Is there a difference between efficient causes in the future, and teleological causes? I am not sure, but I want to suggest that there is a difference here. The teleological cause is oriented towards some end, let us say a natural end. The efficient cause which stands in the ‘later-than’ relation to its effects, however, has no such orientation.
This, however, requires that one agree that there are in the natural world, natural ends (and, ironically, that is the last thing a Naturalist, for instance, would admit – though the Naturalist who is a B-theorist with respect to time may not be able to escape admitting the possibility of efficient causes standing in the ‘later-than’ relation to their effects). However, supposing that God has some end in mind with some efficient cause (standing in the ‘later-than’ relation to its effects), would that suffice to make the efficient cause in question a teleological cause? No, I think not, since God could just as well have some end in mind with any particular efficient cause. We should recognize that the teleological category involves a view of Nature according to which Nature has ‘ends’ which are not assigned to it, but belong to it (which is to say, one does not conceive of nature altogether correctly without conceiving of nature as essentially teleological).
Whether one accepts or rejects teleological causes, one can make a distinction between them and efficient causes standing in the ‘later-than’ relation to their effects.