The Theravādins created their own distinct version of the doctrine of momentariness. They do not seem to have been as concerned as the Sarvāstivādins with the ontology and epistemology of material and mental realities per se. Rather, they were more preoccupied with the psychological apparatus governing the process of cognizing of sense data, and hence with the changing ratio between material and mental phenomena. The Yamaka of the canonical Abhidhamma offers what is probably the first textual oc