The Value of Modal Knowledge
As reflective rational beings, we tend to assume that knowledge of necessity has a special kind of value. Think back to when you first discovered that necessarily 2 + 2 = 4: didn’t you experience this discovery as a kind of revelation—as deep, interesting, and even thrilling? Not only does 2 added to 2 give 4 as a matter of fact, but this could not be otherwise—at any other time, for any other kind of thinking being, in any possible world. It may be useful and informative to discover that there happens to be a cat in the room next door, but it is a discovery of another magnitude that mathematical truths are necessary truths. Modal knowledge strikes us as uniquely valuable and profound—more so than non-modal knowledge of what is actually the case (even mathematically). In philosophy we seek it with particular ardor. But why is that? Why do we find knowledge of necessity so deep and exciting?
One possible answer is that necessary truths are general or universals truths, while contingent truths are particular truths. Thus if a truth is necessary it is true in all possible worlds, while if a truth is merely contingent it is true only in some possible worlds. And universal statements are just logically stronger than existential statements—they entail more. It is more valuable to know a necessary truth because it has more general scope—intuitively, it says more. However, we don’t generally accord universal statements special value compared to singular or existential statements—as in “All the coins in my pocket are silver” versus “Some of the coins in my pocket are silver”. Nor do we reserve special esteem for knowledge of what is true at all places or for all times—unless this reflects a necessary truth. It is not universality as such that has value but universality over logical space, i.e. necessity. The truth of a universal quantification is not itself a reason to prize modal knowledge to the degree that we do.
A quite different suggestion invokes our faculty of knowledge: it is not the modal proposition in itself that is valuable but the faculty by which we know it. We are special not the necessary truth itself. For it is not given to every knower to know necessary truths: you have to be a special kind of being to know such truths. Animals, we may surmise, do not have knowledge of necessary truths, even if they have other kinds of knowledge. Nor do human children have such knowledge until they reach the requisite stage of intellectual maturity. As animals and children may be said to experience lower pleasures not higher pleasures, so they may be said to possess lower but not higher knowledge. They lack Reason or Insight or Intuition or Understanding. Thus modal knowledge is a proof of our unique elevation as knowing beings. However, flattering though this theory may be, it fails to identify the source of value we seek. Let’s accept that we are epistemologically special in virtue of possessing modal knowledge: why does that show that modal knowledge itself is especially valuable? We need to know what it is about the object of such knowledge—what it is that is known—that deserves special esteem. No doubt we are also special for having perceptual knowledge, given that this depends on a highly evolved and sophisticated cognitive system, but we don’t think that perceptual truths themselves (e.g. “It’s raining now”) are especially valuable objects of knowledge. Nor do we accord non-modal knowledge of arithmetic the same status as knowledge of the necessity of arithmetical truths, even though both are beyond the reach of animals and infants. There is something about necessity itself that strikes us as especially worth knowing—as epistemic gold. It is the fact not the faculty that invites admiration.
I think the right answer has an Aristotelian complexion. Knowledge of necessity is knowledge of essence quaessence. It is knowledge of what makes a thing the thing that it is—its nature and definition. This is to be contrasted with knowledge of contingency, which concerns what merely happens to be the case, with what is true by chance. What is contingently true of an object does not penetrate to its inner being, but only to its accidental characteristics. For example, it is only contingently true that I am wearing spectacles—in no way does that define my identity—but the fact that I have a particular brain is integral to being the person I am. Thus when we know a necessary truth we are at the heart of a thing’s being, not merely hovering at its ontological periphery. So knowledge of necessary truths confers knowledge of a thing’s essential nature—its what-it-is-to-be, as Aristotle would put it. This is deeper knowledge than knowledge of the chance properties of an object, those it could easily have lacked. Chance, accident, and contingency—these are the marks of everything that is external to the core being of a thing. We value modal knowledge, then, because we value knowledge of a thing’s intrinsic essential nature. Modal knowledge is ontologically penetrating.
This way of thinking posits two ontological levels to reality–a deep level and a superficial level. At the superficial level, we have the contingent and accidental—that which just happens to be true of a thing but could easily have been otherwise. At the deep level, we have essences and natures—that which could not be otherwise. The fact that we value modal knowledge as we do shows that we recognize the existence of these two levels; in particular, that we accept the existence of a level of reality that goes beyond what merely happens to be. It is a level of permanence, fixity, and immutability. This Platonic-sounding level contrasts with the transitory and ever-changing level, that which may be wiped away and abolished. It is the contrast between chance and necessity. Knowledge of the deeper level of reality strikes us as more valuable than knowledge of the more superficial level. It is harder to obtain such knowledge, and when we obtain it we have a more penetrating insight into reality. Any fool can see at a glance that 2 eggs plus 2 eggs equals 4 eggs, but it takes insight to grasp that it is in the very nature of the number 2 that when added to itself it must equal 4. We could reasonably paraphrase “Necessarily 2 + 2 = 4” as “It is in the very nature of the number 2 that doubling it equals 4”. To know this truth we need to have insight into the essential nature of numbers. We are dealing with a metaphysical truth not just an arithmetical truth. We value modal knowledge because we value metaphysical knowledge, which the concept of necessity enables us to possess.
By way of confirmation of this suggestion notice what happens if we set out to deflate modal knowledge. Suppose we insist that all necessity is just a reflection of conventional linguistic rules, with no bearing on extra-linguistic reality. Then modal knowledge will boil down to knowledge of linguistic conventions and intentions to stick by them. In that case, any special value thought to reside in modal knowledge evaporates, along with the notion of de re necessity. Such a deflationary position is calculated to be revisionist, and is felt to be so. We feel that something valuable has been taken away from us—the idea of reality as composed of things with substantial objective essences, which we might discover. It is the same with nomological necessity: here too the notions of law and causation suffer ontological demotion and epistemological deflation if we decide to restrict ourselves to non-modal concepts (“constant conjunction” and the like). The case is comparable to anti-realist views in ethics and aesthetics. The way we spontaneously understand these domains has been attacked, and we are left with a mere husk of the original article. The disappointment we feel is an indication of our initial valuation: we thought we were dealing with something deep and important, but we have been brought to see that there is much less to it than meets the eye. That is: our intuitive sense of the importance of modality rests open a robustly metaphysical conception of its place in the world. We normally take it that necessity is written deep into the nature of things, and hence deserves our attention and respect; but we may be persuaded (wrongly, I would say) that necessity is nothing but revocable human convention. Our habitual starry-eyed and awestruck estimation of modality has been punctured. Thus we value modal knowledge because we believe (rightly) that it reveals deeps truths about the world. It couples with metaphysical knowledge.
The question of the value of modal knowledge has an immediate relevance to the value of philosophy. For it is a traditional and powerful view that philosophy is precisely concerned with the discovery of essences quaessences. Suppose that view to be true: then philosophical knowledge is characteristically modal knowledge—knowledge that something is necessarily the case. Accordingly, philosophical knowledge has the value attaching to modal knowledge, which puts philosophy in a special place epistemologically. Not to put too fine a point on it, it makes philosophical knowledge superior (in one respect anyway) to scientific knowledge or historical knowledge or any knowledge that is of non-modal propositions. Philosophy provides knowledge of essence qua essence, while other branches of inquiry provide only knowledge of what is in fact the case—knowledge of the actual world not knowledge of all possible worlds. For many of us, that is why we went into philosophy to begin with—because it offers a uniquely deep insight into reality, extending across all of logical space. It tells us how things must be, not merely how things happen to be.