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