2. Four Certainties Consequent to Memory, or to Knowledge of a Past Act

90. Now from the fact that memory is of the past, four things follow that are certain.

The first of these is this, that the remembering power acts after passage of time, otherwise it would not be of the past as past, and this is what the Philosopher says in On Memory 1.449b27-28. The fact that memory acts after passage of time must be understood per se, so that the act of remembering per se follows the remembered thing; and the Philosopher’s words are: “all memory happens after passage of time.”

91. The second is that the remembering power perceives the flow of time between the instant or time when the object remembered existed and the instant of present perception.

92. The third is that the object of memory, when it is the object of memory, is not in itself present, because then there would be no memory of it as past.

93. The fourth is that since the object must in some way be present to the act of memory, and it cannot be present in itself, it must be present through its species, and then the remembering power will be a power of conserving the species, and this in the sense of the total power required for memory. For whether there are two powers, one of which conserves the species and the other remembers, or a single one that performs both acts, I care not; at least there is required for remembering the conserving of the species of the object that can be remembered.