When Feeling Out of Sight: Philosophy's Special Relationship with Unknowability

ABSTRACT

Though all fields of inquiry have to struggle with their own unwelcome truths regarding unknowability, philosophy's relationship with unknowability is special. But philosophy's woes regarding unknowability are all of our woes, since what philosophy reveals as unknowable are pivotal presumptions that are implicated in the general conceptual framework we all presume in pursuing our lives with some minimum degree of coherence. When philosophical reflection reveals that we are not entitled to these presumptions, then our entire grip on coherence seems to loosen. Unknowability then seems not to be localized within some highly specialized field but rather to engulf us globally.

all fields of inquiry have to struggle with their own unwelcome truths regarding unknowability. Even in mathematics, the lone field wherein conclusions not subject to shades of probability extend our knowledge into infinite domains—yes, domains, in the plural, since one of math's conclusions is that there are ascending orders of infinity, uncountable infinities beyond the countable infinity of integers—still, even here where our powers of reasoning allow us to reach so infinitely far, we are forced to confront absolute limits on what we can know. In fact, mathematics being mathematics, we are presented with proofs of unknowability.

And yet, though the unwelcome truths of unknowability are there to confront us in so many fields, philosophy's relationship with the unknowable is something special. To import the language of unhealthy human relationships, philosophy and unknowability might be said to be enmeshed with one another.

This enmeshment has partly to do with philosophy's preoccupation with epistemology, or theory of knowledge. Delving deep into such questions as what manner of justification hoists a belief over the epistemological bar into knowledge, philosophy, like mathematics, has produced its startling demonstrations of unknowability. In fact, philosophy's conclusions are more far-reaching than mathematical truths of undecidability, given that they don't concern esoteric abstractions regarding realms of infinity, but rather hit us smack in the foundational conceptual framework we bring to bear in making sense of the world and ourselves within it.

Wilfrid Sellars called this foundational framework "the manifest image of man," arguing that its acquisition heralded "the coming into being of man," by which I think he also meant to include woman. He writes,

I have given this quasi-historical dimension of our construct pride of place, because I want to highlight from the very beginning what might be called the paradox of man's encounter with himself, the paradox consisting of the fact that man couldn't be man until he encountered himself. It is this paradox which supports the last stand of Special Creation. Its central theme is the idea that anything which can properly be called conceptual thinking can occur only within a framework of conceptual thinking in terms of which it can be criticized, supported, refuted, in short, evaluated. To be able to think is to be able to measure one's thoughts by standards of correctness, of relevance, of evidence. In this sense a diversified conceptual framework is a whole which, however sketchy, is prior to its parts, and cannot be construed as a coming together of parts which are already conceptual in character. The conclusion is difficult to avoid that the transition from pre-conceptual patterns of behavior to conceptual thinking was a holistic one, a jump to a level of awareness which is irreducibly new, a jump which was the coming into being of man.

(1962, 42)

Whether or not one agrees with Sellars that it's in the acquisition of our foundational conceptual framework that we became recognizably human, a foundational conceptual framework is, well, foundational, and problems that flout it will seem perplexing to the point of paradoxical. I have only to mention, in this regard, the name of David Hume. Recall his conclusion concerning our inability to justify a belief so pivotal as to be presumed in all our claims about the objective world, from the most commonsensical to the most scientifically startling, namely that nature is governed by unchangeable laws. This presumption, which Hume called "the uniformity of nature," is implicated in any of our beliefs that extend beyond the reports of the immediate content of our experiences, since it is implicated in the very concept of evidence. And it is precisely this omni-implicated presumption that Hume demonstrates can't itself be justified. It can't be justified by a priori reason in the way that logical and mathematical truths can be. Nor can it be justified by a posteriori reasoning, by appealing to evidence, since any appeal to evidence necessarily presumes the very belief that we are trying to justify, an example of vicious circularity if ever there was one.

To grasp Hume's conclusion is to gasp. It is as if he'd identified an immense black hole of unknowability, sucking in, with irresistibly mangling force, all our claims to knowing what he called "matters of fact and existence." The very distinction between justified and unjustified empirical beliefs—between, say, the laws of nature set forth in Newton's Principia Mathematica on the one hand, and, on the other, explanations given in terms of willful demons and garden-haunting sprites—threatens to disappear into the epistemological black hole of Hume's devastating argument.

It was too radical for his contemporaries to assimilate, and so they didn't. Hume was celebrated in his day as a historian, not a philosopher.¹

But one thinker who did grasp and gasp at Hume's conclusion was Immanuel Kant. Hume, Kant wrote, woke him from his "dogmatic slumber," and in his awakening he produced The Critique of Pure Reason. What Kant proposed in answer to Hume's argument was that the justification for the uniformity of nature derives from the very conditions that make experience possible. The belief in the uniformity of nature must be understood to describe not external nature but rather internal human nature. The mind itself imposes lawfulness onto what it ends up experiencing, and so we can rest assured that sensory experience will of necessity conform to lawfulness. Such an approach, depending not on the contents of experience but rather on the very conditions that make experience possible, is known as transcendental empiricism.

Kant's transcendental empiricism contains both good and bad news. The good news is that the notion of evidence is reinstated, allowing us to endorse the evidence-based order of Principia Mathematica over the lawless chaos of demons and sprites. But precisely because the uniformity of nature rests on the nature of the mind, it implies nothing about the world beyond our minds, and that is the bad news. All our knowledge—even that contained in Principia Mathematica or the theories of general relativity and quantum mechanics that would eventually subsume Newtonian physics—is to be categorized as a branch of psychology. The laws of nature we discover don't access the structure of the world—in Kant's terminology "noumenal reality"—but only the structure of our minds. All we can know of the objective world is that it exists; the rest is unknowable. Kant was able to deny the Humean epistemological black hole only by arguing for another immense black hole into which all knowledge of the world beyond our minds disappears beyond the event horizon.

The lesson here is that epistemology, so central to the concerns of philosophy, accounts for at least part of philosophy's special relationship with unknowability. To bear down hard, in the manner of the epistemologist, on the requirements for knowledge has often inexorably led, one way or another, to unwelcome assertions of unknowability.

But why do I keep saying unwelcome? What's so terrible about confronting the limits of our knowledge? Couldn't it be possible that what the rational mind, privileged by philosophers and scientists, regards as unknowable signals only its own built-in limitations "when feeling out of sight"—a phrase plucked, appropriately enough, from Elizabeth Barrett Browning's Sonnet 43? Perhaps unknowability should be regarded as a call for poetic imagination—for artistic imagination of every kind. Perhaps the cultivated faculties on which artists draw can lead us, in the poet's words, "to the depth and breadth and heights my soul can reach when feeling out of sight."

Though I'm hardly one to denigrate art and the ways in which it can grasp and express important truths, I think that calling on art, poetic or otherwise, to reconcile us to unknowability misses the point of what we mean by unknowability. Consisting as it does in there being truths that can't be known—not by any of us, not at any time, not by any means, including those utilizing the full resources of imagination—unknowability can't help but seem undesirable to that species of African ape that chose for its official designation H. sapiens, from the Latin sapere, to know. Whereas the category of the unknown presents itself as a challenge—disciplines to master, projects to pursue—the category of the unknowable defeats us.²

The Linnaean classification demonstrates how much our quest for knowledge means to us. Why does it mean so much to us? Is it merely our vainglorious aspiration to assert our vast superiority over the other animals, or does it gesture toward something deeper? Hegel wrote, "the aim of knowledge is to divest the objective world of its strangeness and to make us more at home in it" (1830, sec. 194). Though I don't often find myself in this position, I'm with Hegel on this matter. Whatever else we H. sapiens might be, we're a species desperately eager to get our bearings in reality—to use a highfalutin word that the writer Philip K. Dick (1995) brought down to earth by famously defining it as "that which, when you stop believing in it, doesn't go away." Unknowability signifies that reality is holding out on us. That's why Kant's transcendental empirical handling of Hume's problem was regarded by Hegel as no improvement on Hume, since it eternally estranges us from reality. No wonder then that it was a quick leap from Kant's unbridgeable gap between phenomenal and noumenal reality to Hegel's absolute idealism, which denied the unknowability of noumenal reality by denying its existence.

Given what knowledge means to us, we would wish the set of unknowable truths to be the null set, and, in the history of thought, various theories have been proposed that would make it so. Hegelian idealism was one such theory. But no theory has sought more assiduously to empty out the category of the unknowable than logical positivism, also known as logical empiricism or radical empiricism. Proposed between the two world wars by a group of philosophers and scientists associated with the legendary Vienna Circle, over whom the influence of Ludwig Wittgenstein hovered like an absent god, logical positivism argued that all seemingly unknowable propositions are nothing but a kind of gibberish on the order of Noam Chomsky's "Colorless green ideas sleep furiously" (1957, 15).

Chomsky's imaginative word-formation isn't an example of an unknowable proposition because it is no proposition at all. It has the syntactic form of a proposition, but it is, semantically, nonsense—which was precisely Chomsky's point in producing it. Because it is semantic nonsense, it succeeds in saying nothing. Such semantically empty propositions may unleash emotively infused images in the subjective mind, just as passages of music do. But being neither true nor false, they present us with nothing to know, and therefore don't signal any limitation on our knowledge.

And so, too, according to positivism, are all other seemingly unknowable propositions—pseudopropositions all. They are not unknowable but meaningless. The set of unknowable truths is therefore shown to be reassuringly empty. Positivism anoints us H. sapiens summa cum laude, eminently suited to knowing all there is to know. The limits of knowability are the limits of meaningfulness. Even that maddeningly unverifiable proposition at the center of Hume's devastating argument is summarily handled by way of positivism. If it is indeed in principle unverifiable, then it is ipso facto meaningless.

Logical positivism performed its marvelous feat of banishing the unknowable by way of its powerful verificationist criterion of meaning—to wit, the meaning of a (nontautological) proposition is nothing other than the empirical means by which it could, in principle, be verified.³

The "in principle" is important. There might be practical limitations on our attempts at verification. So consider the proposition that intelligent life exists elsewhere in the universe. We know the kind of experiences that would verify this proposition even if, though it be true, there might be insurmountable obstacles blocking our ever having those experiences. All we need know, in order to know what a genuine proposition means, is what would count as verification.

An efficient way of disposing of the unknowable was contained in the positivist theory of meaning. Any proposition whose truth-value necessarily eludes verification—as, say, the bulk of theological and metaphysical and ethical and aesthetic propositions do—is rendered gibberish. Positivism was a philosophical theory prepared to brand as "devoid of cognitive meaning" almost the whole of the history of philosophy. "Metaphysicians are musicians without musical talent," wrote Rudolph Carnap (1959, 80), a founding member of the Vienna Circle.

Propositions argued for by traditional philosophers might seem to reverberate with a higher order of truth. Consider Kant's second formulation of the categorical imperative: Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means to an end but always at the same time as an end. This Kantian assertion might strike you, as it does me, as containing profound ethical insight. But the positivist will have none of this sentimental hogwash. Lacking any possible means of verification, Kant's assertion is as devoid of meaning as "Colorless green ideas sleep furiously."

Positivism has its appeal not only for scientists, who are gratified by being deemed by positivism as sitting on top of the cognitive heap, but also for many philosophers, who can grow bloody sick of their special relationship with unknowability.

But obstacles lay in store for positivism. The positivists were committed to uncompromising criteria of clarity, obscurity being the cloak by which pseudopropositions pass themselves off as profound, and it was clarity that proved to be their proverbially self-hoisting petard. No matter how they fiddled with formulating the verificationist criterion of meaning, they could not get it to include all and only those propositions the positivists were intent on including. Chief among the propositions that needed to appear on the right side of the boundary between meaningful and meaningless were scientific truths. But, alas, it was found that to relax the criterion sufficiently so that all scientific truths are safely meaningful is to allow the tainted metaphysical to come rushing in. There were other vexations as well. For example, the very propositions of the positivist theory of meaning turned out to be meaningless. For these and other reasons, philosophy eventually abandoned positivism.

Nonetheless, positivism remains, for obvious reasons, an appealing theory, most especially among scientists, who still are known to hurl a stentorian "meaningless!" at questions empirically unverifiable. When I was a young student of physics, in the seventies, and we were all being indoctrinated with the positivist approach to quantum mechanics known, in honor of Niels Bohr, as the "Copenhagen Interpretation," any question as to how to interpret quantum mechanics in terms of the actual nature of reality was summarily dismissed with a peremptory "meaningless!" As Richard Feynmann succinctly expressed it, "Shut up and calculate!" Two physicists who defied the injunction, David Bohm and Hugh Everett, were officially marginalized by the field back in the 1950s and 1960s. In fact, Robert Oppenheimer is notoriously reported to have said, "If we cannot disprove Bohm, then we must agree to ignore him," while Hugh Everett, whose Princeton PhD advisor, John Wheeler, demanded that Everett radically modify his dissertation after Bohr nixed it, completed his PhD and then turned his back on academia. The non-Copenhagen, reality-descriptive interpretations they each constructed—Bohmian mechanics and the many-worlds interpretation, respectively—now offer the two major competing interpretations of quantum mechanics among physicists. (Bohm interprets the wave function, which is, mathematically, a complex-valued probability amplitude, as a guiding pilot wave, choreographing the trajectory of every particle, even when unobserved. Everett interprets the wave function as giving the spread of possibilities, all of which are realized on the supposition that there are many worlds.)

And still the positivist dogma lingers on, as Tim Maudlin, a philosopher of physics, recently noted:

Logical positivism is a very attractive view for people who do not want to worry about what they cannot observe. It is ultimately a theory about meaning. … Logical positivism has been killed many times over by philosophers. But no matter how many stakes are driven through its heart, it arises unbidden in the minds of scientists. For if the content of a theory goes beyond what you can observe, then you can never, in principle, be sure that any theory is right. And that means there can be interminable arguments about which theory is right that cannot be settled by observation.

(2018)

So here we are, despite the valiant attempt of positivism to relieve us of unknowability, having to face up to the unwelcome fact of it. We must face up to it in physics, where both Bohmian mechanics and the many-worlds interpretation are compatible with the empirical content of quantum mechanics even though they offer such radically divergent pictures of reality. We must face up to it in mathematics, where we are offered proofs of undecidability, following Gödel's demonstration that mathematical statements are not simply game-playing symbol rearrangements, since it is provable that any system rich enough to express arithmetic is incomplete: there are true propositions that won't be provable within the system. And we must face up to it, perhaps most head-bashingly of all, in philosophy, where at least some of the most central problems appear to be not only deeply implicated in how we regard the world and ourselves within it, but also vexingly insoluble.

The situation regarding these philosophical problems seems to be this: we appear to have all the evidence regarding these problems that we're ever going to get, and still a variety of mutually irreconcilable answers remain possible. If we could still be positivists, this very situation would be grounds for dismissing these problems as pseudo-problems, akin to asking what time it is on the sun (an example of Wittgenstein's); but, alas, only those who haven't bothered to plunge into the technical problems of positivism can feel themselves entitled to this satisfyingly eliminative response. And anyway, how can one legitimately level the positivist charge of meaninglessness against philosophy's problems, when the rigorous fields of mathematics and physics have had to face up to the fact that the limits of knowability are not the limits of meaningfulness?

And the questions that these particular philosophical problems pose aren't far removed from life in the way that, say, the problem of the continuum hypothesis is, which is a mathematical problem concerning the different orders of infinity that mathematics has established.⁴ Really, one can get through life extremely well without ever considering whether there is or isn't an infinite set that lies between the infinite set of integers, with cardinality , and the infinite set of real numbers, with cardinality c. And much the same can be said about the so-called measurement problem of quantum mechanics—the attempt to attach the powerfully predictive formalism of the theory to some coherent description of reality.

In contrast, many of philosophy's problems are, like the Humean problem concerning the uniformity of nature, deeply implicated in the general conceptual framework we presume in pursuing our lives with some minimum degree of coherence. When philosophical reflection reveals that we are not entitled to these pivotal presumptions—even worse, when the more we reflect on them, the less we feel that such facts as we presume are even possible, much less knowable—then our entire grip on coherence seems to loosen. Unknowability, then, seems not to be localized within some highly specialized field of inquiry but rather to engulf us globally. These are problems that are characterized both by what we can call epistemic recalcitrance and epistemic nonlocality.

I know I'm being maddeningly meta in my characterization of philosophical problems, even worse than is usual in philosophy, so I'll try to illustrate what I mean by presenting a few standard philosophical problems that display both epistemic recalcitrance and epistemic nonlocality: the somewhat ironically dubbed "hard problem of consciousness," the problem of personal identity, and the problem of free will.

The formulations of these three philosophical problems don't stand in isolation from our empirical knowledge of the world. Quite the contrary, their formulations are empirically informed. Scientific advances shape the way contemporary philosophy poses these questions—in this sense, there is progress in philosophy, though it's progress that piggybacks on scientific progress. But though scientific advances inform the formulations of the problems, they don't provide their answers, no more than does a priori reason. And that, in a nutshell, is the predicament of so much of philosophy.

So consider what we now call "the hard problem of consciousness," this designation having replaced what used to be called "the mind-body problem." It was scientific advances that provoked the rebaptism, since scientific advances have shown that it is overwhelmingly probable that the brain, and nothing but the brain, accounts for consciousness. At least among most contemporary philosophers, no hypotheses of immaterial substances, à la Descartes, are creditably floated. We know, with reasonable probability, that all the facts of consciousness are facts about the brain, but what we don't know, and can't see our way into knowing, is how this can be so. Everything we learn about the brain—including the mapping of which areas of the brain are associated with which aspects of consciousness—fails to tell us why having a functioning brain feels like something, giving rise to the subjective description of what it is like to be that thing. The only way to know the subjectivity of being a particular brain at a particular conscious moment is to be that particular brain at that particular conscious moment. But if the brain is just a material object, as almost all of us accept that it is, then all that is true of it must ultimately be contained in the description of its matter. The two descriptions—the scientifically objective and the phenomenologically subjective—must be capable of being brought together under one unifying theory. But we have no idea of how to begin to conceive of such a unifying theory. As the philosopher Colin McGinn (1989, 349) rather poetically put the problem, "Somehow, we feel, the water of the physical brain is turned into the wine of consciousness, but we draw a total blank on the nature of this conversion."

Another philosopher, David Chalmers, semi-facetiously rebaptized the mind-body problem as "the hard problem of consciousness" in order to dramatize the unknowability that persists despite all the knowledge that has been yielded, and will continue to be yielded, by such empirical fields of inquiry as neuroscience, cognitive science, and evolutionary psychology. These scientific fields pursue problems that are "easy," not because they don't require impressive theoretical and experimental expertise but rather because they do. In contrast, we don't know the type of expertise that would solve the hard problem of consciousness.

And here, in the hard problem of consciousness, is an unknowability not lying remotely far from human concerns, but rather opening up in the inner being of all of us, deriving from the very fact of our possessing an inner being.

The problem of personal identity is, likewise, one that couldn't be less remote from what intimately concerns us all, namely ourselves. The question is: What exactly is that self? What is it that constitutes the identity of this thing that I am now and that I have been ever since the day I was born (or maybe a bit before that day or a bit after) and will continue to be until the day that I die (or maybe somewhat before that day), but in any case, whenever it shall be, a day that I dread precisely because on that day the thing that I am will be no more?

Is it the identity of the body that makes for the identity of ourselves? But, of course, my body will continue to exist, at least for a while, when I am no more. So then my identity is perhaps to be identified with the thing that my living body is, or at least became, at some point in its continuous development from fertilized egg. But isn't the identity of my body the same whether it is living or dead? For my body to pass from the state of being a living body to the state of being a dead body is, to be sure, a radical change, but still, aren't these states of the same thing? This change from living to dead is surely of the greatest significance to me, who ceases to be, but not quite the same thing for my body.

So perhaps then the identity of the body is not the right way to approach the identity of the self.⁵ Perhaps it's rather the unifying inward sense of the self, and so a matter of consciousness that offers the right way of apprehending the identity of the self. It's not that the sense of self is to be identified with any particular state of consciousness that persists just so long as I do. (Hume is famous for exploding the idea that there is any such persistent state of consciousness coexistent with our existence.) Rather I am to be identified with that which, though not necessarily presented within consciousness, nevertheless unifies those states of consciousness by being able to access them from the inside, with that unmistakable feeling of their being mine. I am the thing that remembers my past experiences, often with feelings of regret, remorse, or shame, believing myself to have been responsible for the mistakes that same self that I am now committed in the past and hoping to learn from them, since I am also that thing that cares about my future self and its welfare and shapes my intentions accordingly. Memory and intentions, together with a myriad of self-referential emotions, all point to my sense of owning my states of consciousness across time. I am, in short, the thing that owns my states of consciousness, and you are the thing that owns your states of consciousness.

But this inward-based criterion of personal identity also falls victim to a host of problems. Often these problems are expressed in terms of thought experiments involving brain transplants, which present us with two different persons who each claim to be identical with the same person. From the inside both have equal claim to being identical to that person, though they are clearly not identical with each other.⁶

Stay with this problem long enough, and the sense of paralyzing perplexity is sufficient to have caused some celebrated philosophers to argue that there is no fact of the matter regarding personal identity, no fact that determines when I begin and when I end, no fact that distinguishes me from you. Personal identity is not an all-ornothing kind of thing, but rather consists of similarity, a relation that admits of degrees.

So imagine that as I age, the interests and ideas that once meant so much to me—and provided the coherence and continuity in my life as I worked single-mindedly to make progress regarding them—gradually fade away in my mind, while at the same time they continue to be vividly apprehended and pursued by students to whom I'd transmitted those interests and ideas. The person I once had been will be more identical to my once-students than to the person whose brain, though physically identical with the brain that once had pursued those interests and ideas, no longer contains a trace of them.

The prominent English philosopher Derek Parfit held something like this view, though he confessed that it was "unstable," and that he had to keep reinforcing his rejection of the fact of the matter of personal identity by running, once again, through the arguments that led to his asking how can any such fact as this even be possible? Now, to my way of thinking, this last question typifies the confounding situation presented by many philosophical problems, and so what Parfit brilliantly demonstrates, with the profusion of the thought experiments he devised that deepened the confusion surrounding the fact of personal identity, is that personal identity is indeed a doozy of a philosophical problem.

And last of all we consider the problem of free will. In speaking just now of personal identity, I mentioned that I sometimes recall past experiences with feelings of regret, remorse, and shame, holding myself accountable for actions I'd done that I judge—maybe even judged back then when I committed them—as morally reprehensible. These are thoughts and emotions that all but psychopaths experience. To experience these thoughts and emotions is to feel that one could have done otherwise and so to regret that one didn't.

But are all of us, with the exception of psychopaths, confused in our believing that we could have done otherwise? After all, there either was or wasn't an explanation for why I did what I now regret. Let's suppose there is an explanation for the causes of my wrong action, which will be in terms of the kind of person I am. In turn, the kind of person I am will be explicable by way of both genetic and environmental factors, embedded in a causal network that provides the fuller explanation for why I did what I did. How then could I have done otherwise, given that my action was explicable? But if my action is inexplicable—if it can't be entirely explained in terms of the kind of person I am because some random factor intervenes—then in what sense can it even be said to have been my action? Each horn of the dilemma leads to the same conclusion: I couldn't have done otherwise, in the one case because I couldn't help being the person that I am who did the wrong, and in the other case because the person that I am has nothing to do with the wrong that I did.

In addition to the issue of moral accountability, such reflections as these also undermine our belief that we ever make any decisions at all. All our experiences of trying to decide what to do, from the most trivial—shall I order the fattening dessert?—to the most agonizingly consequential, are mere illusions. It might appear to us, by way of introspection, that we are wrestling with our choices, but this is yet another example of introspection's fallibility.

The philosophical confounding settles around the fact so deeply implicated in our lives that in certain situations we might have acted otherwise. It's this counterfactual proposition that, the more we reflect on it, the less possible it seems. And yet will any of us thereby cease to struggle with our decisions or continue to behave as nonpsychopaths, holding ourselves accountable for the actions we perform? The very idea of giving up on our agency seems to make life seem hardly worth living.

These are three epistemically recalcitrant philosophical problems, and there are more where they came from.⁷ Like Hume's outstanding problem, they identify a proposition that is deeply implicated in the presumptions we make in pursuing our lives, which, on reflection, seems not only to be unknown but unknowable. But precisely because this unknowability hits us smack where we struggle to make sense of ourselves and the world, what we end up experiencing is epistemically nonlocal.

What is it that philosophers do in the face of such confounding? Is there anything more to be done, in confronting such philosophical problems as these, beyond grasping and gasping? There certainly is, as the history of philosophy bears out. I'll use the problem of free will as my paradigmatic example in illustrating the various options a philosopher might choose beyond grasping and gasping.

A philosopher might proceed by identifying the philosophically problematic concept or proposition with another, relatively unproblematic one. Colin McGinn calls this "domesticating" the problem (see McGinn 1993). So, for example, the "compatibilist solution" to the problem of free will analyzes the proposition "I acted freely" to mean that I did what I wanted in the absence of any obstacles standing in my way. Say I'm a bank manager who empties out the bank's cash reserves, but only because somebody is pointing a gun at my head. In such a situation I'm regarded as not having acted freely and so am not held responsible. The compatibilist domestication of the problem of a free will clarifies the notion of legal responsibility, further suggesting that we ought to satisfy ourselves with this clarification of the legal distinction, it being all that we, practically speaking, require.

Or the philosopher might attempt, so to speak, to "sci-dye" the problematic concept or proposition, by identifying it with some aspect of a mind-blowingly counterintuitive scientific theory. Quantum mechanics comes in handy here. In the case of free will, the stochastic nature of the laws of quantum mechanics has been enlisted to help the philosopher out.⁸

Perhaps the philosophical response will come by way of reification—an argument for another largely unknown, though not necessarily unknowable, level of reality beyond the known physical level of observation and theoretical science. The reified level, in its distinctiveness from the physical, is hopefully able to accommodate the problematic concept or fact. So perhaps the appeal to desires and beliefs, in explaining actions, can be seen as just such a reification, pointing to a type of mental causation distinct from physical causation, and therefore one that isn't subject to the binaries of determinism versus indeterminism that characterize the physical.

Or the philosopher might seek to eliminate the problematic proposition—perhaps appealing to a scientific theory that explains away the problematic fact, as, say, modern theories of abnormal psychology explain away the notion of certain irrationally behaving people being possessed by the devil. So for example, a philosopher might argue that agency and accountability don't exist at all, but are merely illusions installed in our brains by natural selection to deliver the adaptive benefits of group cooperation.

Or perhaps the philosopher might "epistemologize" the problem, trying to demonstrate that, though there is nothing intrinsically difficult about these particular philosophical problems, they are difficult for us, given the particular foundational conceptual framework we bring to bear on reasoning things out, whether empirically or analytically. After all, our conceptual framework—Sellar's manifest image—is a product of natural selection, just as our physical form is. The physical form with which natural selection bequeathed us makes certain activities impossible for us—flying, for example. Why shouldn't the conceptual framework with which natural selection bequeathed us have made certain problems the intellectual analogues of flying? A good place to sample these analogues is in the syllabi of philosophy courses, or so the epistemologizer suggests.

Noam Chomsky and Colin McGinn are two contemporary thinkers who have developed the epistemologizing approach by offering an account of our cognitive framework that makes its natural limits explicable (without removing them). In brief, both see our acquisition of combinatorial principles as fundamental to not only our linguistic competence⁹ but also our intellectual competence. (McGinn also adds as essential to our cognitive setup our perceptual faculties, most centrally vision, in yielding us spatially continuous representations.) These two systems, linguistic and intellectual, are each combinatorial, meshing with each other in such a way as to allow us to say what we think. The fact that they are combinatorial allows for the considerable creative freedom manifested in both systems, but it also imposes a limiting factor. "In other words, cognitive accessibility is a function of similarity to the concerns of our linguistic and perceptual faculties; crucially, it turns upon the applicability of the combinatorial paradigm supplied by language" (McGinn 2004, 189).

McGinn uses this epistemologizing approach, which he calls transcendental naturalism, to explain why philosophical problems have proven to be so intractable. Just as there could, in principle, be noncombinatorial languages that, though meaningful, would be unlearnable by us—think the inkblot language used by the aliens in the movie Arrival—there could be propositions that, though true, can't be rendered unproblematic for us, given the combinatorial intellectual setup we've inherited. Some examples of such problematic propositions might be: I am a material thing with an inexpressibly rich inner life. I am one distinct thing, and not another, who came into existence at some time t and will go out of existence at some time t+n. I am an agent who deliberates over what to do and what to believe and is to be held accountable, both by herself and others, for those beliefs and actions.¹⁰

Last of all, the philosopher may theologize, an approach no longer as popular as it once was. Alone of all approaches, theologizing welcomes unknowability. Like epistemologizing, it focuses on the intrinsic limits of our intellectual setup, attributed not—as in the Chomsky-McGinn account—to the accidents of natural selection, but rather to our finitude. Unable even to make sense of the free will without which our life as moral agents is inconceivable, we are forced to posit the numinous infinity of God in which all mysteries and paradoxes are ultimately resolved. (The theologizer regards God in much the way that the reifier regards the nonphysical.)

Domesticating, eliminating, sci-dyeing, epistemologizing, reifying, theologizing: arrange them in the right order and we have DESERT, an acronym that strikes me as grimly apt. The very plurality of the approaches attests to philosophy's enmeshment with unknowability at a deeply human level. Which of the approaches a philosopher settles on—and then develops with all the philosophical finesse at her command, so that again, within the borders of an approach, there can be progress—depends, to some extent, on what could be called philosophical temperament, which, among other things, determines which hypotheses about both reality and ourselves she is even willing to consider. Coupled with the diversity of approaches is a diversity of intuitions.

But now we have moved from philosophy to psychology, which is a move often made by none other than Hume. Typically, after having demonstrated why a belief couldn't be justified—the uniformity of nature, the fact of personal identity, the existence of the external world—he would turn to psychology to explain why we nevertheless continue to believe with undiminished conviction, or vivacity, as he called it. The arational psychological mechanisms he hypothesized (heavily relying on an associationist model of the mind) were, Hume thought, shared by all of us. To invoke temperament is to insist, in contrast, that individual variability plays a significant role in filling the gap between, on the one hand, exhaustive conceptual analysis and available evidence, and, on the other, conviction.

That a psychology of diversity is in play in how we do philosophy was a theme of William James, who, of course, straddled the two fields of philosophy and psychology. He wrote,

The history of philosophy is to a great extent that of a certain clash of human temperaments. Undignified as such a treatment may seem to some of my colleagues, I shall have to take account of this clash and explain a good many of the divergences of philosophers by it. Of whatever temperament a professional philosopher is, he tries when philosophizing to sink the fact of his temperament. Temperament is no conventionally recognized reason, so he urges impersonal reasons only for his conclusions. Yet his temperament really gives him a stronger bias than any of his more strictly objective premises.

(2000, 8–9)

Philosophers still tend to take offense at the suggestion that temperament functions more prominently in philosophy than in other fields, for the suggestion seems to psychologize the discipline. And yet to deny the role of temperament is to deny how deeply philosophical problems strike in the manifest image of H. sapiens. It's philosophy's special relationship with unknowability that gives individually variable temperaments and intuitions a lively, if hidden, role to play in reaching for the depth and breadth and heights our souls can reach when feeling out of sight—or not.