 Crathorn develops his position mostly by attacking the views of other philosophers who accepted such distinctions, but unfortunately he is not always clear about his positive reasons for abandoning Aristotelian ontology. But, on one hand it is consistent with his epistemology, for our only direct and natural certitude is that qualities exist. On the other hand, it is also consistent with his frequent tendency to materialism. Indeed, we can discern hints of atomism in his Commentary on the Sentences.