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Dreams and the Physiology of Memory in Aristotle’s Parva Naturalia

Claire Coiro Bubb

This paper uses Aristotle’s treatment of the physiological process of dreaming in the Parva Naturalia to illuminate his beliefs about the mechanisms of memory and recollection. Aristotle categorizes memory and recollection as activities of sensation (450a14) and reason (453a10-14), respectively, but he is also clear that both are physical phenomena (450a30-b11; 453a14-21). However, he nowhere offers a coherent explanation of the physical details. As a result, scholarship has not focused on the physical aspect of memory, but rather on the manifold other issues raised in De Memoria. I propose a hypothetical physical model to fit his theories of memory and recollection, using parallels from his discussion of dreams to help fill in the blanks.

Aristotle defines memory in De Memoria as the possession of a perception after time has passed and he couches his discussion of the recollection of these memories in terms of physical movements. However, he only offers details on the mental processes required to initiate and control recollection, rather than explaining the attendant physical phenomena. In De Insomniis he defines the images seen in dreams as ‘percepts’ or faint remnants of the various things sensed during the day. These remnants are present in the blood stream, but unnoticed during the day when they are overshadowed by the immediate sense impressions being delivered to the common sensorium by the sense organs. They are similarly overwhelmed for part of the night by the turbulent digestive process, which he also locates in the bloodstream, but, once digestion is complete, the sense remnants become appreciable and make up the stuff of dreams. I point out similarities of concept and language in order to suggest that memories consist of these same sense remnants, filed away with a sort of ‘time stamp’; further, I speculate that this process of internalizing and cataloguing memories is a kind of second, psychological digestion that happens during dreaming, after the digestion of food. This would be an appropriate moment for memories, which are ‘not present while experience is present’ (451a24-5), but exist only ‘whenever time has passed’ (449b25), to be established and to be inserted into the matrix of other memories within which the process of recollection occurs.

This theory, that the remnants of the day's active sense perception are digested into memories and catalogued during sleep, addresses a variety of puzzles in the Parva Naturalia. It accounts for the time lapse that is intrinsic to Aristotle’s definition of memory. It clarifies the mechanism of the recollection of memories, which he explicitly identifies as a physical process (σωματικόν, 453a14). The process of recollection involves a domino-like movement from one idea to another until you arrive at the intended object of recollection, presupposing that memories are stored in a rational, almost linear, fashion according to their similarity, opposition or nearness (451b19). This theory suggests how randomly experienced memories could attain such an organization. By positing a second, non-nutritive phase of digestion, my theory solves the inconsistency that arises from his claims that both dreams (461a7, 461a27) and awaking (458a21) are the direct result of the completion of digestion. It thus also provides the function of sleep, which he insists upon but never identifies, that differentiates it from other forms of unconsciousness. It even helps restore sense to a usually emended manuscript reading at 461a22 and 461a27 concerning the coherency versus robustness of dreams. Indeed, though the location of the process in the heart and bloodstream make it seem more like science fiction, modern science supports the idea that learning is internalized while we dream.

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Aisthêsis: Sense and Sensation in Greco-Roman Medicine

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