This is no proof that mutation is motion in the internal parts of the body. Hobbes needs to argue that it is logically necessary and sufficient for large-scale change that there be a change in the relative positions of a body's particles. Necessity and sufficiency seems to be put over by Hobbes's saying that mutation is, rather than that mutation involves, disarrangement of the internal parts. He does not argue for the necessity and sufficiency claim. He asserts the weaker proposition that an undisturbed arrangement of a body's parts is sufficient for its appearing to be the same or unchanged over time. Besides being open to counter-examples he gives in other connections, and being weaker than the necessity and sufficiency claim he needs, the proposition he asserts speaks of a body's appearing to be unchanged when what is at stake is real, not apparent, sameness or change.