  According to Dietrich quiddity is properly defined as the formal determination of a being, giving it its specific intrinsic character by means of which it can also be known. Strictly speaking, therefore, quiddity is found only in composite beings since it implies a formal aspect of a being. Unlike Aquinas Dietrich will not allow quiddity to designate the whole composite, even if the designation is understood to be abstract. Strictly speaking, therefore, quiddity is not applied to simple beings. Maurer suggests that the reason for this is Dietrich’s adhering closely to Aristotle who in the seventh book of the Metaphysics maintains that predication with respect to quiddity must be of another thing, hence of a composite, because it answers the question why “this” of “that”? There must be a “that” in order meaningfully to ask the question “why this?” In everything having a quiddity it is thus necessary that there be a distinction between the quiddity and that which possesses the quiddity.