 Whether an item is a continuous or contiguous whole will depend upon other metaphysical commitments. Some early medieval philosophers only have simple artifacts like fences and walls in mind when they talk about contiguous wholes. But others think that even more complicated man-made objects, such as wagons, houses, and clocks are contiguous, and not continuous wholes, because only substances are continuous wholes. Abelard and Aquinas both hold the latter position, and thus, that only individual donkeys, palm trees, human beings, and the like, are continuous wholes. Abelard thinks that this is true because only God can fuse parts together into a continuous unity. Human manipulations, no matter how skilled, are only capable of placing parts in close proximity to one another (Dialectica 417.4–37; 419.35–420.6). Drawing upon Aristotle’s reflections on form and matter (especially in his De Anima, Physics and Metaphysics), Aquinas thinks that only substances possess the kind of form that can inhere in each and every part of the whole and thereby make it truly one (Summa Theologiae I, q. 76, art. 8; Quaestiones de Anima q. 10; see also Pasnau 2002, 79–88). An artifact possesses a form that merely orders and arranges the parts of the whole. We can tell whether a form imbues its parts in the manner required of a substantial form by attending to the effect of the form’s existence on the functionality of the parts. The human soul inheres in the hands of a human being as a substantial form because if the soul were removed, that part would cease to function as a hand – indeed, Aquinas insists that this thing would cease to be a hand. By contrast, when the form of a car is removed from the items that make up the car, many of these items can still be car-parts. For example, a carburetor can still be a carburetor; it can be placed in another car and continue functioning as a  carburetor.[2]