ultimately, we needn’t ask where memory is preserved. Certainly not in the brain, according to him. If the brain serves any purpose, it’s merely as a recall instru-ment—filtering, selecting, and fixing memory as image. The past is preserved by itself, automatically! But at the risk of repetition: how does this apply to the distinctive physionomy of a single memory? How is lived duration, containing as it does its own preservation principle, preserved in the form of individualized memories rather than the heterogeneous continuum it otherwise represents? How does the flow of experience transform into memorable moments?

This question remains insoluble if framed on a single reality plane. Bergson’s pro-posal firmly distinguishes the virtual character of memory considered in itself, which he refers to as “pure memory,” [souvenir pur] from its multiple actualizations as consciousness-presented memory-images. Between these actual and virtual planes, memory forms a “dynamic schema” deploying across differentiated planes of consciousness, corresponding to various degrees of depth and intensity, dif-ferent levels of organization. Memories are extracted from an unstable, floating mnemonic matter that Bergson describes as “nebulosity,” a pre-individual field constituting the past’s very medium:

“Whenever we are trying to recover a recollection, to call up some period ofour history, we become conscious of an act sui generis by which we detach ourselves from the present in order to replace ourselves, first, in the past in general, then, in a certain region of the past - a work of adjustment, something like the focusing of a camera. But our recollection still remains virtual; we sim-ply prepare ourselves to receive it by adopting the appropriate attitude. Little by little it comes into view like a con- densing cloud; from the virtual state it passes into the actual; and as its outlines become more distinct and its surface takes on color, it tends to imitate perception. But it remains attached to the past by its deepest roots, and if, when once realized, it did not retain something of its original virtuality, if, being a present state, it were not also something which stands out distinct from the pres-ent, we should never know it for a memory.” (Matter and Memory, op. cit., pp. 133-134)

“Nebulosity” doesn’t equate pure memory with an indeterminate or overdeter-mined object, in the sense suggested by the “superposition” of quantum states before measurement. Rather, it returns memory to the past’s very medium, beyond any actual determination. We spontaneously turn toward this medium whenever we make the effort to remember. It’s truly a medium, not a substrate or support: nebulosity is not the carrier of actualized images revived in conscious-ness through recall, but the milieu from which they are extracted. More simply, it designates memory’s modality before actualization happens. There’s no question of returning to pure memory as a template or prototype for memory actualized as image. This, by the way, explains why we can’t easily trace memories back through a continuous causal chain to the source-events that triggered them. Here lies the true source of the difficulties faced by contemporary causal theories of memory.

To conclude, let’s briefly examine the mechanism of voluntary recollection:

“When we let our memory wander at random, without effort, images succeed images, all situated on the same plane of con-sciousness. On the contrary, as soon as we make an effort to remember, it seems that we gather ourselves at a higher level to then descend progressively toward the images to be evoked.” (Henri Bergson, «Intellectual Effort,» in Mind-Energy, New York, Henry Holt, 1920 p. 201).