  Dietrich’s account of quid and quiditas is more limited. He takes up these concepts in his De quiditatibus entium. Where ens, entitas, esse, and essentia are all existential terms answering the question whether something exists, in the De quiditatibus he considers the question “What is it that exists?” He begins the treatise by distinguishing quid and quiditas from the existential terms, and then proceeds to consider the differences with respect to being in substance, in logical concepts or intentions, and in accidents. Again, unlike Aquinas who equated essentia and quiditas, Dietrich sees these metaphysical concepts are being different, but not totally unrelated.And while Aquinas accepts the separability of accidents, Dietrich rejects the notion.