  A plausible rationale for the Sarvāstivādin’s  assertion of the continuing existence of past and future  dharmas concerns the first and third arguments: it is  impossible to conceive of a non-existent intentional object or the  causal efficacy of a non-existent dharma. Given the  principle of momentariness, which states that things exist only as  point instants, it would be impossible to explain the arising of a  particular type of cognitive awareness in the absence of an already  existing preceding cause. Cognitive awareness, which arises in  dependence upon the object and the corresponding sense faculty, would lack support if past dharmas were unreal. In his commentary to  the verse portion of the Treasury of Higher Knowledge,  Vasubandhu explains the standpoint of the Sarvāstivādin as  follows: 