For another, because the premises from which this immortality of the mind may be deduced depend on an explanation of the whole of physics, which would show, first, that all substances whatever things, that is, that have to be created by God in order to exist are of their own nature incorruptible, and can never cease to exist, unless they are reduced to nothing by the same God's denying them his support; and, secondly, that body in a general sense is a substance, and never perishes; but that the human body, in so far as it differs from the rest of bodies, is constituted purely by a certain arrangement of parts and by other accidents of the same kind; whereas the mind is not composed of any accidents in this way, but is a pure substance.