  Reid grants that perceptions, memories and imaginings often differ in degree of force and vivacity, but, he argues, this difference is insufficient to account for the special quality of presentness represented in perceptions, the special quality of pastness represented in memories, and the special quality of atemporality represented in imaginings (Inquiry, 197). While memories may be faint, or weak, these features are not necessary to these states being memories, and so cannot be used to individuate them. In addition, a present idea—whatever its degree of force and vivacity—cannot ground judgments about events in the past because present ideas represent events as present.