Also the beauty of nature, _i.e._ its connexion with the free play of our cognitive faculties in apprehending and judging of its appearance, can be regarded as a kind of objective purposiveness of nature in its whole [content] as a system of which man is a member; if once the teleological judging of the same by means of the natural purposes which organised beings suggest to us, has justified for us the Idea of a great system of purposes of nature. We can regard it as a favour[110] which nature has felt for us, that in addition to what is useful it has so profusely dispensed beauty and charm; and we can therefore love it, as well as regard it with respect on account of its immensity, and feel ourselves ennobled by such regard; just as if nature had established and adorned its splendid theatre precisely with this view. We shall say only one thing more in this paragraph. If we have once discovered in nature a faculty of bringing forth products that can only be thought by us in accordance with the concept of final causes, we go further still. We venture to judge that things belong to a system of purposes, which yet do not (either in themselves or in their purposive relations) necessitate our seeking for any principle of their possibility beyond the mechanism of causes working blindly. For the first Idea, as concerns its ground, already brings us beyond the world of sense; since the unity of the supersensible principle must be regarded as valid in this way not merely for certain species of natural beings, but for the whole of nature as a system. § 68. _Of the principle of Teleology as internal principle of natural science_ The principles of a science are either internal to it and are then called domestic (_principia domestica_), or are based on concepts that can only find their place outside it and so are _foreign_ principles (_peregrina_). Sciences that contain the latter, place at the basis of their doctrines auxiliary propositions (_lemmata_), _i.e._ they borrow some concept, and with it a ground of arrangement, from another science. Every science is in itself a system, and it is not enough in it to build in accordance with principles and thus to employ a technical procedure, but we must go to work with it architectonically, as a building subsisting for itself; we must not treat it as an additional wing or part of another building, but as a whole in itself, although we may subsequently make a passage from it into that other or conversely. If then we introduce into the context of natural science the concept of God in order to explain the purposiveness in nature, and subsequently use this purposiveness to prove that there is a God, there is no internal consistency in either science [_i.e._ either in natural science or theology]; and a delusive circle brings them both into uncertainty, because they have allowed their boundaries to overlap.