 Kant goes into more detail about the notion of a natural purpose in §65, where he specifies two conditions something must meet in order to be a natural purpose. The first, that the “parts are possible…only through their relation to the whole” (§65, 373), is a condition on something’s being, not only a natural purpose, but a purpose tout court. It thus applies not only to living things but also to artifacts, such as watches, in which each part is there for the sake of its relation to the whole, and is thus in a sense there only on account of its relation to the whole. The second condition, which applies only to purposes which are natural, is that “the parts of the thing…are reciprocally cause and effect of their form” (ibid.). (This corresponds to the third of the features to which Kant drew our attention in the example of the tree at §64.) This condition is not met by artifacts, a point which Kant illustrates by appeal to the example of a watch, whose parts, unlike the parts of a plant or animal, do not produce one another or maintain one another in existence.