An Illusory Ideal of Philosophy

Against Causal Epistemology

It has been suggested that knowledge of the natural world enjoys a causal foundation not enjoyed elsewhere. Thus such knowledge is deemed intelligible while other kinds are not. Accordingly, we can accept a notion of robust truth in relation to propositions about the natural world while other kinds of proposition must remain under suspicion of non-truth. Empirical science emerges as both true and knowable while mathematics and morals make dubious claims to truth and knowledge.[1]It would be mysterious how we can have knowledge in the latter two cases, given that their subject matter doesn’t causally interact with our cognitive faculties. We must therefore seek some sort of non-cognitive account of those areas, accepting that knowledge is impossible as far as they are concerned.

I propose to question this bifurcation at its root: causal epistemology is a misguided idea, applicable nowhere; it therefore provides no standard whereby we can judge other domains of thought and discourse. It isn’t just that causal epistemology isn’t generally required for respectability and intelligibility though it delivers those virtues in the case of some domains. Rather, there is really no such thing anywhere—it is a chimerical ideal. These are subversive claims given a longstanding orthodoxy, but they serve to undermine subversion in areas that matter to us.

The idea of causal epistemology includes a picture and a promise. No one supposes that we currently possess a complete causal account (explanation, science) of human knowledge acquisition in the case of our knowledge of the natural world, but the idea of such an account is supposed to make us feel safe about human knowledge in the areas to which it applies (though not in others)—it provides a reassuring picture of what is going on. The promise is that this picture will be converted into a full-blown causal theory of how knowledge is acquired, which will vindicate such knowledge. The world makes a causal impact on our sense organs via physical stimuli (light, sound, pressure, chemical diffusion) and as a result we form beliefs about the world outside our skin. Empirical knowledge is an effectof physical stimuli; the causal relation puts us in “contact” with the world beyond, mediating between mind and reality. For example, I know that there is a cup on my desk because the cup on my desk is causing me to believe it is there: it is operating causally on my senses and my nervous system transmits this operation to my belief centers. Thus the connection between belief and fact is rendered intelligible; thanks to causation we canknow such things. Moreover, this causal connection can be investigated by the empirical sciences, thus “naturalizing” such knowledge. By contrast, nothing like this is possible with respect to putative knowledge of mathematics and morals: numbers, sets, and moral values don’t causally impinge on us, generating the kind of “contact” required for knowledge. Such knowledge would be altogether mysterious and unintelligible; and so the truth status of mathematical and moral claims is brought into question.

But the picture and the promise are precisely that—they are programmatic. Moreover, they are deeply mistaken about how empirical knowledge works. First we must make an important distinction—between the existenceof a causal relation between belief and fact, on the one hand, and our having knowledgeof such a relation, on the other. There is all the difference in the world between the cup’s causing me to believe in its presence and my thinkingthat this is so. This bears on the question of what my reasonfor belief is: is it that I seem to see a cup or is that I think that a cup is causing me to seem to see it? The latter suggestion is problematic: I don’t normally have such thoughts (I may even reject them); they presuppose the very item of knowledge they are supposed to ground (that there is a cup on my desk); and it is obscure how they can be explained in the favored causal terms—for how can the existence of a causal connection between a part of the world and my mind itself be a cause of a belief of mine? How does causation produce knowledge of causation, and how does the mind register psychophysical causation? No: the reason I have for forming my belief about the cup is simply that I have an experience as of a cup—not that I have an experience as of a cup causing me to believe in it (whatever that might mean). I have various sensory experiences as of the world being a certain way, and they function as my reasons for forming beliefs about how the world is. The concept of causation does not enter my deliberations or the reasons that figure in them. If there are such causal relations, they are not part of my reasoning process. My belief is justified to the extent that I have good reasons of this sort, but these reasons don’t advert to causal relations between mind and world.

This raises a natural question: does it matterwhether such relations exist so far as knowledge is concerned? Granted they do, but what is the relevance of that to epistemology as a normative enterprise? Here is a quick way to see the problem: suppose we abrogate the normal causal relations that (we believe) obtain between natural facts and our beliefs about them, replacing them with some other sort of relation—does that abolish knowledge? Suppose we postulate a pre-established harmony between belief and fact, superintended by God or Nature, with no causal interaction between mind and world, but exhibiting reliable counterfactual-supporting connections. By hypothesis there is no causal epistemology applicable to beliefs formed in this world, yet it is hard to deny that knowledge can exist in it: people have reasons based on their experience and there is a reliable link to truth. What if our world islike this (as Leibniz thought): does that mean no empirical knowledge is possible? Hardly. The ingredients necessary and sufficient for knowledge are present; it is just that there is no causal dependence between world and mind. The existence of causal dependence is thus extraneous to knowledge. What if physics abandons the notion of causality (as some have claimed it should): does that mean knowledge also undergoes defenestration? Rational reasons for belief would still exist in the shape of sensory evidence, despite the absence of causal relations.

We should also note that causation by itself is never sufficient for knowledge and has nothing intrinsically to do with knowledge. The world is constantly impinging on our bodies, but it doesn’t generally produce knowledge thereby. Most of the time we don’t even notice it. And certainly causal interaction between inanimate objects has no tendency to produce knowledge in them. Epistemology is normative, but causality is not. Reasons are not merely effects. Nor is it true that a belief is simply triggered by an outside stimulus; belief acquisition operates against a background of other beliefs that are normatively relevant (“holism”)–it is not just stimulus-response psychology. Then there is the old problem of deviant causal chains. Suppose there exists an opaque barrier interposed between me and the cup preventing any light from it reaching my eyes, but by some strange quirk of nature the cup releases a chemical that enters my skin and causes me to hallucinate a cup (I know nothing about this). We have here a causal dependence between my belief and the cup—but do I knowthere is a cup in front of me? I don’t seethe cup despite the causal connection, and it is doubtful that I have perceptual knowledge in this situation (why, is an interesting question). It can’t be just any old causal connection that leads to the kind of cognitive “contact” deemed essential to knowledge. Then too there is the question, bequeathed to us by Hume, of whether causation itself is intelligible: do we really know what causation is? Causation involves necessary connection, but isn’t that epistemologically problematic? Is knowledge of causation a secure foundation for epistemology? What if we can’t really know causation as it exists in objects? What if causation is itself a mystery? The causal theorist is remarkably sanguine about the epistemology of causation. Maybe all we are entitled to is the notion of contingent correlation, so that any attempt to invoke full-blooded causation is a mistake. It is certainly not a notion free of puzzlement.

And there are the notorious difficulties concerning inferential knowledge. Not all of empirical knowledge is of singular facts that we can observe by means of the senses; some things we must infer. But these things are not the causes of our beliefs, so the causal theorist must resort to an indirect way of extending the causal theory in their direction (consider knowledge of the future). Knowledge of generalizations is particularly problematic, since general facts don’t impinge on our senses (e.g., laws of nature). Really the causal theory applies at best to a small subclass of knowledge claims—those that concern directly perceptible particulars. The rest get consigned to hand waving. The case of introspective knowledge is instructive: we don’t sense our own mental states yet we know about them. So we can’t apply our (rudimentary) causal understanding of sense perception to introspective knowledge: my pain doesn’t transmit physical signals to a special sense organ that enables me to perceive it. Whether the causal account of knowledge can be extended to introspective knowledge is a moot question; yet it is hard to deny that the mind makes “contact” with its own inner states. Knowledge of what I am now thinking hardly fits the supposed paradigm of perceptual knowledge: isn’t it just a straight counterexample to such a theory of knowledge in general?

The upshot of these considerations is that a causal theory of knowledge hardly sets the standard for respectable epistemology. It is really just a vague picture of the mind linking itself to reality. This is not how knowledge works generally, and even in the cases most favorable to it there are serious problems. So it can’t be a point of criticism of some putative area of knowledge that it fails to live up to the high standards demanded by causal epistemology. So what if mathematics and morals fail to conform to the causal model? That model is defective even in the areas it is designed to cover. It is just massively tendentious to demand that other kinds of knowledge imitate this supposedly perspicuous model. Knowledge comes in many forms, covering many subject matters, and each form obeys its own distinctive principles and methods—perceptual, introspective, inferential, general, innate, logical, mathematical, modal, moral, aesthetic, political, historical, psychological, etc.[2]Reference is much the same, and it would be equally misguided to insist that all reference conform to the case of reference to a perceptible particular. Maybe it is hard to devise a theory of reference suitable for all types of reference—and similarly for all types of knowledge—but that is no reason to deny that reference and knowledge have wide (and univocal) application. Equally, it may be that these concepts give rise to genuine mysteries, but again that is no reason to deny that they apply to the real world. We should not seek to deform (or reform) our ordinary understanding of a region of thought or discourse in an effort to squeeze that region into the causal model, given the problems inherent in that model (“theory” is too grand a word). We shouldn’t try to revise the semantics of a piece of discourse just because we can’t see how to subsume it under a causal model derived from another piece of discourse. Knowledge varies with the subject matter and is as heterogeneous as it is.

Colin McGinn

[1]This issue is raised by Paul Benacerraf in “Mathematical Truth” (1972).

[2]This pluralist position is advocated by T.M. Scanlon in Being Realistic About Reasons(2014).