themselves and apart from any relation to other things, can be thought as possible only as purposes of nature. Hence they first afford objective reality to the concept of a purpose of nature, as distinguished from a practical purpose; and so they give to the science of nature the basis for a teleology, i.e. a mode of judgement about natural Objects according to a special principle which otherwise we should in no way be justified in introducing (because we cannot see a priori the possibility of this kind of causality).