Knowledge, Memory, and Time
We have knowledge of the past, the present, and the future—or we think we do anyway. That makes three types of knowledge, classified according to time. But when you think about it you see that there is really only one type of knowledge: knowledge of the past.  Knowledge of the future is based on knowledge of the past; it has no other source. We know what has happened so far and we project this knowledge into the future, relying on inductive inference. Knowledge of the future is simply knowledge of the past extrapolated forward: if there were no knowledge of the past, there would be no knowledge of the future. Knowledge of the present, so-called, is also really knowledge of the past: for it takes a finite time for a stimulus to cause a percept, and it takes a further finite time to form a belief based on a percept. By the time you have formed a belief about what is presently the case it may no longer be the case. This time lag is notoriously writ large in the case of distant astronomical objects: by the time you have perceived and formed a belief about such objects they may be long gone. Our knowledge is always of the past, though we may project it forward by making present-tense judgments, hoping that things haven’t changed too much in the interim. What we know is always strictly about what has been (this is true even for introspective knowledge, since it too takes time to formulate). In the most basic cases our knowledge is a trace of the past—an effect of a prior cause. In fact, there is always a complex sequence of events mediating the outside stimulus and the knowledge it eventually produces—events that are both computational and physiological, occurring in the nervous system. These function like memories of earlier events in that they involve holding information for later processing: the retinal image is a kind of memory of the light pattern that reaches the eye, and subsequent neural patterns are like memories of the retinal image. There is information storage over time, though the time might be measured in milliseconds.
Given that memory is the retention of information over time, we could say that all knowledge, including present-tense knowledge, is based on memory. Indeed, the light pattern that reaches the eye from a distant (and possibly extinct) galaxy might profitably be viewed as itself a type of memory of the galaxy in question: for the light preserves information about that galaxy over time, possibly for many years. The universe remembers! If we were to go externalist about memory, we could include this kind of information retention in the mechanisms of memory: the light preserves information about a remote object and then the nervous system of the observer preserves information contained in the light. In any case we have information preservation over time, the mark of memory. We can simplify matters theoretically by stipulating that the process of belief formation elicited by past events is a memory process: information retention is always a type of remembering. Even when an object is right in front of you now there is a complex memory process as information is gleaned, processed, and stored—eventually leading you to form a belief about the object (“This is red”). Subjectively it all seems to happen in an instant, but in fact there is always a time lag between the object having the property and the observer coming to know it has that property. If we were being very careful (the skeptic looking over our shoulder), we would more cautiously assert only that the object was red, albeit a fraction of a second ago. The sensory modules inside us, which have a much more fine-grained experience of time, might confine themselves to judgments along the lines of “I seem to recall that such and such an event happened in the recent past”. By the time the light stimulus makes itself felt in the visual cortex at the back of the head, after a long trip through the optic nerve and the brain, the retinal image might be a distant memory as far as our visual processors are concerned. The essential point is that information retention is the method whereby knowledge of the present is acquired—that is, knowledge of the past. In short, all knowledge is memory knowledge. When the positivists spoke of “observation statements” as forming the epistemic bedrock of science (and not just the positivists), they misspoke: it is memories of observation that form the basis of scientific knowledge. Observation itself is essentially a memory process, but in addition the observation must be retained over time, in memory and by means of external record (e.g. writing). The real basis of scientific knowledge is memory: no memory, no science. Everything we know about the world must be contained in what we remember about it. Our knowledge of the future and the present is really nothing but our knowledge of the past plus some inferential moves (more or less dubious according to the skeptic).
The question must then arise as to how good memory is as a source of knowledge of the world. Does memory tell us how the world really is? Memory is, of course, notoriously unreliable, subject to distortion, fleeting and fallible. It needs some kind of external check if its deliverances are to be credited—and the checks too need somehow to be remembered. But that is not the point I want to emphasize: I want to focus on a deep structural feature of memory—what memory constitutively is. This feature is somewhat elusive to characterize, though we all recognize what it is; it tends to be described metaphorically or impressionistically. Hume spoke of memory images as “faint copies” of sensory impressions, which are vivid in comparison—as if memories are faded and worn, indistinct and blurry—and this description carries intuitive appeal. We might say that memories are impoverished or etiolated or drained of substance or sketchy or fragmentary or thin or insubstantial. Marcel Proust is the poet of memory as a feeble route to the past: it simply cannot recreate the psychological effect of past experience itself (this is why we are in search of lost time).  Only the madeleine can bring back the past, enabling us to relive it, and even that cannot really recall the past experience in all its glory. Time past is time irrecoverable. Let me put the point this way: memory cannot provide us with a mode of apprehending the world that captures its full reality. Memories of the past are glancing, stripped down, and partial–ghostly remnants of what they purport to record. They are mere traces, like footprints in the sand: they don’t afford us the kind of full brimming knowledge of the past for which we yearn. They are not like seeing or touching or tasting something: remembering a taste is not like tasting a taste. It is true that some people reportedly experience the past in this quasi-perceptual way, and normal people can sometimes have remarkably vivid memories, but generally memory is a feeble conduit for knowledge of the past. It is normally pretty thin gruel. And once we appreciate the role of memory in perceptual knowledge we start to wonder how much is omitted even there: maybe a lot of information is lost between stimulus and response—even Humean impressions might be drastically etiolated compared to reality itself. If memory images are faint compared to sensory impressions, sensory impressions might be faint compared to the objective world; indeed they presumably are, given that enormous amounts of information don’t even get beyond the initial sensory receptors (the retina is by no means locally omniscient). We can conceive of creatures that have super vivid sense impressions, compared to which ours are pale and weak. In any case human memory is just not very saturated or all encompassing. And if memory is limited in this way, our knowledge must be too, proceeding as it does from such a bleached out basis. Our conception of reality is formed from our memories of it when you get right down to it, but memories are just not very rich or full or penetrating. Just think of your general conception of the past: it is shadowy, reduced, distant, full of blanks, and skeletal–even when operating at its most efficient. You really can’t think of the past as it is in itself (this was Proust’s lifelong lament). The past is gone, epistemically speaking; it is fundamentally irrecoverable, even when memory is accurate. The past is a shadow world (Plato should have used the parable of the cave to illustrate the feebleness of memory). But our conception of the world derives from memory and inherits its limitations. You might suppose that perceptual experience offers a way to something more vivid—more real—but don’t forget that experiences themselves become objects of remembering. Memories of experiences are themselves weak and faint, nothing like having the experience (and even that suffers from time lags and limited information retention). Fundamentally, our whole picture of the world is conditioned by our powers of memory, but memory is ineluctably Proustian—it can only offer us so much lost time.
Our epistemic relation to time is all out of whack: we can’t grasp time while it is happening, so to speak. Time is not obliging to human knowledge—not the past, not the present, not the future. We are always late to the party (or much too early in the case of the future), and poorly dressed and equipped. Time and human knowledge are just not cut out for each other. The result is that we view reality through a misty portal, a narrow and smoky window. This means that we never really grasp reality as it is, de re as it were; at best we form ideas that map its structure, or we feel its effects on our consciousness. God doesn’t remember the past, as if at a distance from it; he perceives the past—feels it in his marrow (or the divine equivalent). Think of an animal’s memory-mediated conception of reality, say a mongoose’s: that must be thin gruel indeed. Fortunately the animal is equipped with a bunch of instincts and doesn’t need to rely on abstract knowledge; we on the other hand fancy ourselves endowed with intellectual apprehension, while actually laboring under the constitutive limitations of memory. Memory is frustratingly flimsy, a perpetual source of existential angst, a Proustian nightmare. It all comes down to memory for us, but memory is very far from all there is. Reality itself has no truck with memory limitations and won’t agree to be represented by memory. Reality has all the talent and its agent memory is but a weak and impoverished echo of it. The past is always much more than memory can ever know. 
 I will put aside questions of innate knowledge; our concern here is with acquired empirical knowledge. A prioriknowledge is not temporally bound and is not founded in memory, but empirical knowledge of the world needs memory-assisted sense perception to get off the ground.
 There is a good discussion of this philosophical theme in Proust (who was influenced by Bergson) in Nabokov’s Lectures on Literature (1980). Nabokov writes: “To recreate the past something other than the operation of memory must happen: there must be a combination of a present sensation (especially taste, smell, touch, sound) with a recollection, a remembrance, of the sensuous past… In other words, a nosegay of the senses in the present and the vision of an event or sensation in the past, this is when sense and memory come together and lost time is found again.” (p.249) I would add that such recreation can never be complete. Memory alone cannot do the job, so we need to supplement it with the more vital and full-blooded force of perception; but this combination is still impotent to produce the impact of direct past experience. Thus we search in vain for lost time: the past comes to us only in hints and morsels, despite that magical madeleine. The only way truly to recover the past is to travel back to it—and then we are still stuck with the memory-like nature of perception.
 Here we might speak, not so much of cognitive closure, as of cognitive claustrophobia—the feeling of being squeezed into a space too confined, cognitively speaking. This is the prison of memory: the way knowledge is held in check by the very nature of the memory faculty. And it is not just a matter of what is remembered but of the wayremembering works—that faintness, that etiolation, that fatal thinness. The world for us is a remembered world, but remembering is subject to extremes of deletion and dilution. The veil of remembering (as opposed to the veil of perception) is an apt metaphor: the past hides coyly behind this veil, showing itself only sketchily and dimly. This must condition the way we think of reality.