If then all natural things are analogous to the snub in their nature eg nose, eye, face, flesh, bone, and, in general, animal; leaf, root, bark, and, in general, plant (for none of these can be defined without reference to movement they always have matter), it is clear how we must seek and define the essence in the case of natural objects, and also why it belongs to the student of nature to study (E) soul to some extent, ie so much of it as is not independent of matter.