from this principle, we cannot know with certainty whether several parts of the form which is now apparent in a species have not a contingent and unpurposive origin; and the principle of Teleology, to judge nothing in an organised being as unpurposive which maintains it in its propagation, would be very unreliable in its application and would be valid solely for the original stock (of which we have no further knowledge).

Hume takes exception to those who find it requisite to assume for all such natural purposes a teleological principle of judgement, i.e. an architectonic Understanding. He says that it may fairly be asked: how is such an Understanding possible? How can the manifold faculties and properties that constitute the possibility of an Understanding, which has at the same time executive force,