Logic and Morality
Are there any affinities between logic and morality? The question may appear perverse: aren’t logic and morality at opposite ends of the spectrum? Isn’t logic dry and abstract while morality is human and practical? Isn’t one about proofs and the other about opinions? I think the affinities are real, however, and I propose to sketch them. Both concern guides to conduct: how we should behave, cognitively and practically. Logic gives rules to reason by; morality gives rules for action. These rules purport to be correct—to yield valid reasoning and right action. Thus logic and morality are both normative: they tell us what we ought to do. They are not descriptions of what we actually do but prescriptions about what should be done. These prescriptions can take a number of forms: on the one hand, logical laws, rules of inference, and avoidance of logical fallacies; on the other hand, moral laws, rules of conduct, and avoidance of immoral actions. Thus we have the three classical laws of logic (identity, non-contradiction, and excluded middle) and the utilitarian principle, or a list of basic duties (corresponding to consequentialism and deontology). We also have rules for making inferences: modus ponens and the Kantian principle of universalizability, say—as well as warnings against fallacious inference (don’t affirm the consequent, don’t try to infer an “ought” from an “is”). Neither subject is concerned to establish “matters of fact” about the natural world; both are concerned to improve reasoning, make us better people, keep us on the right track. It is good to reason validly and to do what is morally right. Thus logic and morality are procedural and prohibitive, rule-governed and critical. We apply them to facts in order to produce desirable results—true beliefs, right actions—but they are not a form of fact gathering analogous to physics or history. They are practical not theoretical. They are active and engaged not laid-back and detached.
It would be wrong to contrast the two in respect of formality. It is true that we have formal logic as taught in university logic courses, while morality can scarcely claim anything comparable (though there is deontic logic). But the logic and morality I am talking about are pre-formal—they are embedded in our natural competence at dealing with the world and are probably innately based. Logical reasoning existed before Aristotle tried to codify it, and morality pre-dates attempts at explicit refined statement. These are primitive forms of human competence, not dissimilar to language competence before grammarians came along. The distinction between logic and morality is relatively recent and may not have been salient to early humans. We know quite well what is meant by the “ethics of belief”, and we are not shy about pointing out fallacies in other people’s moral reasoning. Sound reasoning is sound reasoning—and it is what we should be aiming at. The distinction between logic and morality is not as sharp as we tend to think these days (I suspect it is less sharp in the ancient world than in the post-Christian word). Shoddy logical reasoning is deplored, as immoral action is. You should keep your promises and you should follow modus ponens; we can worry about fine points of logic versus morality later. If we suppose that animals possess rudimentary forms of logic and morality, are they really distinct modules in the animal mind? Logic and morality bleed into each other.
Where does prudential reasoning fit? It is surely only logical (rational) to consider one’s own future wellbeing—so we might assign prudence to logic. But prudence is also behaving well to one’s future self, so that it falls within morality. Some moralists have even supposed (I think rightly) that prudence is a special case of morality—we have moral duties towards ourselves, as one sentient being among others. So prudential reasoning is both logical and moral—it has a foot in both camps. Or should we say that the idea of a dualism of camps is mistaken? Isn’t the line more blurred than contemporary culture recognizes? We think there is no morality in logic textbooks and that moral issues can’t be resolved by formal logic: but that is surely too narrow a view of both fields. Logic is up to its ears in normative notions, and morality is a domain of logical reasoning. If you are trying to resolve a complex moral issue, such as abortion or animal rights, you will find yourself invoking principles drawn from logic and from normative ethics—as we currently understand those fields. But from a ground level perspective these distinctions are blurred and irrelevant: you are just reasoning with whatever bears upon the topic. You are applying your logical and moral competence to a real world problem with a view to doing what is right. When you avoid deriving an “ought” from an “is” are you doing logic or morality? When you declare that all sentient beings have rights is that intended as a moral principle or a logical one? It functions as an abstract axiom used to draw conclusions—it is irrelevant whether it crops up in a standard logic text (they don’t even include modal logic). We shouldn’t have too narrow a view of logic, and we shouldn’t neglect the abstract character of much moral reasoning. I am inclined to say simply that moral reasoning just is logical reasoning—logical reasoning about questions of value.
What about the point that logic is fixed, rigid and universal while morality is changeable, fluid and relative? Isn’t morality controversial and logic indisputable? But this is a naïve and tendentious way to think: logic has its controversies and morality is a lot more universal than many people suppose. I won’t rehearse the usual criticisms of moral relativism, subjectivism, emotivism, etc.; suffice it to say that morality is really a subject in objectively good standing. Also, logic is not free of internal strife: some find modal logic suspect, others favor intuitionistic logic, still others adopt a highly inclusive conception of logic (even accepting logical contradictions). Not much in human thought is not controversial in some way. Skeptics of the normative will object to “ought” in both logic and morality, but that simply underlines the affinity of the two areas. The essential point is that both logic and morality are normative systems designed to facilitate desirable outcomes; and both admit of a degree of formal articulation rooted in intuitive human faculties. We can all agree (if we are sane) that pain is bad and everything is identical to itself: why one should be assigned exclusively to something called “logic” and the other to something called “morality” is obscure. Both are self-evident propositions capable of functioning as axioms in a train of reasoning: the affinity is more obvious than the difference. You should keep your promises and not be cruel; you should existentially generalize and not affirm the consequent. Where exactly is the deep difference here? And this is before we get to non-standard logics like modal logic, epistemic logic, indexical logic, and deontic logic. They are all about reasoning and validity—but so is morality about reasoning and validity. If morality is about moral reasons, it is about moral reasoning: but then it is a logical enterprise. Logic is capacious enough to subsume morality, being the general theory of sound reasoning.
Recognizing the affinity is helpful in resisting certain deforming conceptions of moral language and thought. Emotivism, prescriptivism, naturalism, psychologism, non-cognitivism, Platonism, contractualism: are any of these remotely plausible when applied to logic? People have toyed with such accounts of logic, but generally they have not found favor, so why should we seriously entertain them for morality? Moral discourse is like logical discourse—objective and normative—and should be treated as such. It is what it is and not some other thing. Thus its similarity to logic can work to legitimate it and avoid procrustean and reductive reinterpretations. Notably, the difficulty of finding justificatory foundations applies to both areas—some things just have to be taken for granted (pain just is bad, modus ponens just is correct). And in so far as logic should not be construed as a descriptive science of the platonic realm but as a normative system of rules of correct reasoning, so morality should not be thought of as describing the Good but as a normative system of rules of right action. If we cleave to the logical analogy, we can steer our way through dubious assimilations and deformations. Just to simplify matters, I recommend that we assert outright that morality is logic (part of it anyway): that way we have a neat antidote to various bad ideas about morality. This does not remove all philosophical questions about morality, but it raises the right kinds of questions. Logic, too, raises real philosophical questions, both metaphysical and epistemological, but these questions are the right ones to raise concerning morality. Morality, we might say, has a logical structure—and a logical role. It functions logically. Logicism is true of it (“moral logicism”). But I also think that logic needs to shed its antiseptic image and confess to its normative heart: it is really about how we should reason, what goodreasoning is. To be sure, we can treat logical systems formally, as mathematical objects; but the thrust of logic is prescriptive and critical—evaluative. It is concerned with a certain human value (viz. good reasoning), and therefore naturally belongs with morality. It is part of “value theory”. Accordingly, it belongs with such practices as praise and blame, conscience and shame, reward and punishment, respect and disrespect. An illogical person is not a moral person; irrationality is a vice. Moral goodness and logical goodness are inseparable attributes, seamlessly connected; indeed, we shouldn’t even speak in such disparate terms. The distinction between logic and morality is an untenable dualism, an artificial separation.
 Thus the tradition has supposed both logic and morality to be known a priori, possibly to be synthetic a priori. This leads to reactionary attempts to demystify them: logic consists only of tautologies and morality is cognitively empty.
 In fact, I don’t believe there is a non-arbitrary definition of logic (or of logical constant) that separates off one kind of entailment from others, but I won’t go into this now.
 The awe and reverence Kant felt for the moral law has its counterpart in an idolatry of logic—as if logic has a godlike status (there should have been a Greek god dedicated to logic). This is logic as something sacred and sublime (to use Wittgenstein’s term).
 It may be useful for designing an academic curriculum but it doesn’t capture the real nature of our logical and moral being. Both are expressions of our underlying rationality.