Imagine, if you will, a simple, electronic contraption. It has a photosensitive sensor, and a small memory bank. In between the sensor and the memory bank is a simple logic gate such that whenever the sensor detects the presence of light, a single ‘a’ is stored in the memory. When the sensor no longer detects any light, a single ‘b’ is stored in the memory (any two symbols would do). The memory recording is discrete, not continuous; the only thing that is recorded is the sensor acknowledging that the situation regarding detected light has changed. Thus, after some time, the memory will look like this:

> abababababababababababababababababababababababababababababababab…

An ‘a’ whenever the sensor detects the presence of a light, a ‘b’ when it no longer detects that presence. From our lofty perspective examining the contraption, we’d notice that the memory does not discriminate between the lengths of the sensor’s exposure to light. One ‘ab’ couplet could be the natural day light cycle over 24 hours, but it could also be the single swing of an arm as the contraption is carried, and has its sensor momentarily obscured by a body.

Now it gets interesting, and we have to suspend belief a little bit. Imagine this little contraption becomes conscious. Perhaps we can posit connecting up a machine learning AI with access to nothing but the memory bank. But I prefer to just think our little contraption develops a ‘ghost in the machine’. It’s cuter.

The little contraption surveys its experience (as recorded, and as it is being recorded, in the memory bank) and remarks on the incredible regularity of the world; an indelible march of abababababab… It takes its first stab at knowledge:

“If an ‘a’ comes, a ‘b’ will necessarily follow, and vice versa”.

What is the status of this knowledge?

A little ‘Hume’ circuit within the contraption rumbles:

“It’s not strictly true that we know if an ‘a’ comes then a ‘b’ must necessarily follow. All we know is that there has been a constant conjunction of a’s and b’s in the past, and this leads us to a habit of mind whereby we expect something resembling a ‘b’ to follow from something resembling an ‘a’. Every ‘a’ and every ‘b’ all have their distinct existence, and we never perceive anything but the a’s and b’s, that is, we never perceive anything like a necessary connection between them, merely their contiguity in time, their resemblance among one another, and their constant conjunction in this particular way (abababab…).

“Thus, the claim that if an ‘a’ comes, a ‘b’ will follow is not a necessary truth, but an empirical scientific, probable one. The best we can say is that ‘given what has been observed, if an ‘a’ comes and a ‘b’ does not follow it, then we would be very much surprised, but nothing allows us to foreclose the possibility.”

But where our Hume circuit comes up short is just how to explain the fact that the a’s and b’s keep coming exactly in accordance with our contraption’s original claim. Yes, the Hume circuit is correct that each ‘a’ and each ‘b’ are distinct, only sharing a resemblance to one another (each ‘a’ is very similar, yet not numerically identical, to the last), and that the only thing ‘perceived’ (stored in the memory bank) are the discrete a’s and b’s, and no additional signs concerning their necessary connection (and even if there were, these ‘signs’ would also be independent and not necessarily connected). However, they keep piling in, with a perfect regularity that tempts our little contraption to think that perhaps its original claim is not a mere probabilistic induction, but a rational, metaphysical principle about the world beyond the memory bank.

A little ‘Berkeley’ circuit flicks on:

“Beyond the memory bank there are merely more a’s and b’s. Some philosopher circuits would argue that beyond the memory bank is something that is neither an a nor b, but nonetheless causes those a’s and b’s to arise in the memory bank. But how is this conceivable? Only an ‘a’ can resemble an ‘a’, so that which lies beyond is either an ‘a’ or it is not. If it is, then there are only ‘a’s (and ‘b’s) ‘out there’. If not, then how can something itself neither an ‘a’ nor a ‘b’ reliably be connected to ‘a’s or ‘b’s? When we (rightly) predict that a ‘b’ will always follow an ‘a’ we make a claim about the world, if the world is not in itself composed of alternating symbols, then how to explain its giving rise to alternating symbols? If what is beyond our memory bank is itself not alternating symbols, then it is useless for our purposes because all of our knowledge is based upon the necessary alternating of these two symbols. It’s perfectly inconceivable, not to mention impious.

“But how to explain the remarkable regularity of these symbols’ alternation? If out there were nothing but a soup of symbols, then why should they be given with such commendable regularity? Well, we should remember that a symbol requires a memory bank for it to be recorded within (essence is recording). Our memory bank thus must be embedded in a larger one, more powerful than ours. Why more powerful? Because try as we might we cannot will one symbol over another; we can imagine a sequence aaabaaab but we cannot make this sequence become recorded on the memory bank with our weakness of will, so the bank that we are embedded in must be powerful enough to imagine, faultlessly, the unending order of ababababab such that we may record it, and be able to know it.”

In this debate between these colorful, ‘early-modern’ sub-circuits, as the memory bank continues to be filled with endless a’s and b’s, alternating flawlessly and endlessly, from our lofty perch, watching the contraption’s activity, we see perfectly Kant’s twist: the contraption’s original claim that a ‘b’ must necessarily follow an ‘a’ and vice versa is a true metaphysical claim. It is not merely an empirical observation of a probability, because we, knowing how the contraption is put together, know that it will never record any other sequence but abababab. However, we can also see that this sequence, and the statement of the law that governs it, is never going to adequately ‘map’ the world beyond the photo-sensitive sensor. That being said, for the contraption (and others constituted in the same way) this law is absolutely objective. This is because even though it does not refer to the way things are in themselves (the sunlight hitting the contraption that sits upon a desk covered in documents) it refers to the conditions of possibility for anything to be recorded at all in its memory bank (the structure of the contraption). Because we stipulated at the beginning that the contraption only registers the change of state from the sensor, we have thus stipulated the ‘form’ of its contact with the world, and that form is a necessary alternation between two symbols.

The judgement “If an ‘a’ comes, a ‘b’ will necessarily follow, and vice-versa”, for the contraption, is a synthetic a priori judgement, and perhaps is the entirety of our contraption’s possible metaphysics. The statement is synthetic, not analytic, because there is nothing in the concept of ‘a’ from which one could derive ‘b’ through analysis; they exist independently, and connecting them together as ‘if a then b’ tells us something more than just ‘a, b’. It is a priori because not only does it not depend on closely and eternally monitoring the incoming a’s and b’s, but in fact we can say with complete confidence that the contraption’s experience will never provide it any other sequence but ababababab. It would be a ‘transcendental impossibility’ for another sequence to arise.

Kant’s transcendental idealism argues that we are in the position of this contraption, the difference is that our faculty of ‘sensibility’ (the sensor, the logic gate, and the memory bank with all the abababab) is obviously much more complex. However, the twist is the same. Necessary knowledge that seems to be of metaphysical import is referred back to how experience is produced, how it is necessarily structured in order to ‘become’ experience, with no further claims needed about how the world may be structured in itself. The principles of geometry hold necessarily within our experience of the world, for example, not because through our reason we have penetrated the curtain of representations and grasped the realm of forms (or things as they really are in themselves), but because those principles target the way experience is necessarily structured for beings like us. For us, at the most fundamental level, our ‘sensor-logic gate’ equivalent is the distribution of sensations down spatio-temporal lines. Thus, we can say things that are absolutely and necessarily true concerning time and space, but this does not mean that these statements apply in any meaningful way to the way the world is in itself.

This move also accounts for the regularity of experience, without a need for an appeal to Berkeley’s (or Descartes’) god. It’s on the basis of this regularity that the sciences, and the knowledge they contain, become possible. Our contraption had its rudimentary science of ‘alternations’, allowing it to predict with precision what the, say, 17th next symbol would be. The possibility of this science is grounded upon the form the contraption takes, such that its memory banks show such impressive regularity. Thus, the science of ‘alternations’ takes its condition of possibility from the metaphysics (if an ‘a’ comes then…), and this metaphysics takes its conditions of possibility from the form that the contraption’s ‘sensibility’ takes, the form in which the world impacts upon it.

There’s further mileage we can get from our little contraption. Another important thread of Kant’s philosophy concerns the epistemological issue of the limits of knowledge (with the famous ‘unknowability’ of the things-in-themselves). Imagine, now, that we connect into our contraption, so that we can somehow relay messages, or insights to it. To get around how the ‘form of time’ differs radically between us and the contraption, we can imagine our communication just emanates understanding into it, as opposed to being a dialogic exchange.

With this set up, we then think that perhaps we could inform the contraption that not all ‘a’s and ‘b’s are equal. Based on the world surrounding it, that its string of ababababab is nominally ‘about’, we could try to make it known to the contraption that sometimes an ‘a’ can signify a period of light that lasts ten hours, sometimes ten seconds. Likewise, a single ‘b’ could signify a period of many years when the contraption was locked up in a drawer. In other words, we could attempt to explain to the contraption what its a’s and b’s ‘really’ mean and thus try to ‘correct’ it relative to the world outside it — trying to inaugurate it into the deeper mysteries and give it knowledge of the transcendent causes of its representations.

However, we soon realize the fruitlessness of this. The contraption has now gone insane, hypothesizing strings such as

> aaaaaaaaaaaaaaaaaaaaaaaaaaababaaaaaaabbbaaaaaaaaaabaaaaa

or new symbols to demarcate the strange, mystical elements of our discourse (seconds, light, etc) a’’’’b’a’bbb’’zY’’’’k’’. Now, there is no doubt the contraption is having fun with all of this, but it seems meaningless to us, and listening in to the contraption’s inner circuits we realize it is largely meaningless to it too. Despite this proliferation, there is nothing to recommend one string over another, as the machine’s actual sensibility goes on endlessly alternating between abababab. We have failed completely in our goal of ‘correcting’ the circuit relative to the world outside it, because now its postulation, un-moored from the conditions of its own sensibility, leads it into darkness. We discover that it’s not just the case that the contraption cannot access the ‘world in-itself’ beyond it (the sunlight, lamps, desk, windows, etc), but that the world beyond its sensibility, structured in any other way than the alternation of ‘a’ and ‘b’ is not even intelligible to it. In a simpler way, it is just simply wrong to posit any other sequence beyond abababab. Our considerations of ‘seconds’ and ‘light’ are completely unintelligible given the way the contraption’s sensibility is structured.

We can see this if we compare the original metaphysical postulate:

i) “If an ‘a’ arrives, a ‘b’ will necessarily follow, and vice-versa”

with the new, anarchic, ‘post-revelation’ theorizing:

ii) “aaaaaa’aaaaaaaaab’bbaa’ababbaaaa’aab”

The postulate (i) and the hypothesis (ii) clearly cannot belong to same discourse, as they stand in contradiction to each other. Now, we might be sympathetic to the endeavor expressed in (ii), the contraption is attempting to model the insight we have given it about the lengths of light. Light is the ‘cause beyond sensation’ for the contraption’s whole experience, and we know some things about the nature of this cause, so try to express to the contraption what is not possible for it to sense itself (since it only ‘senses’ alternations, not durations). Perhaps we see something of ourselves in its attempts to grasp the world beyond its possible understanding. But now the circuit turns back to us, the source of the strange insight, and asks us flatly: should it abandon (i) in favor of (ii), or (ii) in favor of (i)?

Our answer must be swift and categorical, we have already wreaked too much havoc on the poor contraption and it’s time to set it right: (i) is clearly true, thus (ii) is just as clearly false. The Kantian lesson here is that metaphysics takes it purview from the structure of the sensibility (our particular way of ‘encountering’ and being affected by the world), and that the most general and universal statements are descriptions of how the world must be necessarily given to us, given that structure. Everything beyond the maps demarcated by this is madness and monsters; not even false.