A set-theoretical definition of the physical memories of stimuli

Presumably, the memory of a stimulus exists as a difference in a system due to that stimulus, compared to what the system would have been had the stimulus never occurred. Thus every stimulus, to be remembered, must define with the system a set of phenomena perfectly divergent from those of other stimuli. Therefore there exist no subsets of physical phenomena common to memories of different stimuli, even those the experimenter classifies as equivalent. It is concluded that human awareness of groups of stimuli requires a dualistic explanation.