The difference between rationality and rational self-interest

by Massimo Pigliucci

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Far too often in the course of discussions on this blog or with friends I encounter a fundamental confusion: people using the word “rational” (or “irrational”) as if there were only one clear meaning of it, from which their own position follows logically (or, alternatively, other people’s position is therefore deemed illogical). Not so.

The ancient Greeks had already made a distinction between “theoria” (theoretical reason) and “praxis” (practical reason), the first one being the sort of reasoning that is supposed to reflect a point of view from nowhere, as the phrase goes, while the second one is a type of instrumental rationality deployed in the pursuit of specific ends. (Yes, modern philosophy and cognitive science have respectively argued and shown convincingly that human beings can hardly access a view from nowhere, but it is an ideal, meaning that in some cases we want to transcend as much as possible our foibles and specific issues to look at the world as broadly as is feasible for us.)

While all systems of logic do need starting assumptions (or axioms, as they are called in math), and no interestingly complex individual system can be completely justified from within itself, the aims and assumptions of theoretical and practical reason are nonetheless clearly distinct. Theoretical reason is what we deploy when we wish to arrive at general principles of logic that apply regardless of the circumstances (e.g., the principle of non-contradiction), while the practical reason tells us what we need to do in order to maximize a specified utility function.

Of course, much of the confusion I referred to above comes in when I have discussions with libertarian-oriented people, who never fail to bring in rational self-interest, or the principle of rational egoism, as a trump card. We don’t need to get (again) into Rand-style pseudophilosophy here, as rational egoism was seriously discussed (and criticized) by Henry Sidgwick in his The Methods of Ethics already in 1907. One of the things that is often confused by libertarian/objectivists is that there is a fundamental distinction between rational egoism (a type of reasoning) and ethical egoism (an ethical position). One can readily agree that rational egoism is a particular kind of instrumental rationality (i.e., it isn’t “irrational”) without having to concede that it is ethical (I certainly don’t).

Indeed, this distinction between the (instrumental) logic and the ethics of one’s actions is one of the issues that makes economics such a fascinating field. Pace the most scientistically inclined of my readers and commenters, as this is one area where we clearly see the difference between facts and values. (Yes, I am aware of Quine’s denial of that distinction, I think that Quine is over-interpreted and over-rated in this respect. At best, he was able to argue that the difference isn’t always sharp, not that it doesn’t exist.)

I think of economics as a type of (soft) social science, not as quackery, despite the fact that much nonsense is being sold to us all in its name by a variety of pundits and experts. I mean that there are facts about economies that we can’t (or shouldn’t, at any rate) ignore, regardless of our values about fairness, distribution of wealth, etc. But it is also obvious that what is “rational” in economics does not depend only on those facts, it greatly depends on one’s values and how the latter determine one’s priorities. So, for instance, it may very well be that laissez-faire capitalism is the best way to maximize distribution of goods (I am not conceding the point, I am assuming it for the sake of argument), but even so we could (should, really) decide that other criteria need to be counted into the equation too, and sometimes may even override the goal of maximization of distribution (or even, gulp!, of maximization of shareholders’ profits). Criteria such as fair access to resources (like education and health care), safety, environmental impact, and so forth are among those that might be considered.

So, one cannot simply assume without argument that rational self-interest is equivalent to rationality tout court. Firstly, because it is a particular type of instrumental rationality whose assumptions may (should) be questioned. Secondly, because there are other uses of instrumental rationality available (such as maximizing societal benefit, enhancement of human flourishing, etc.). Thirdly, because it isn’t the type of general rationality that seeks principles independent of particular points of view (i.e., it is a type of praxis, not theoria).

Let me take up another example, which concerns issues that have arisen during the (ongoing) preparation of a collection of essays on the philosophy of pseudoscience that Maarten Boudry and I are putting together for the University of Chicago Press. It hinges on the following question: can we reasonably (ah!) say that it is rational to align one’s beliefs with the available evidence (a la Bayes theorem and Hume’s dictum)? Most skeptics would say hell yes, and repeat the Hume-inspired Sagan mantra: extraordinary claims require extraordinary evidence.

Yes, but that is true from the point of view of theoretical reason. Cognitive science has begun to show that human beings apparently need to believe, at least some of the time, in things for which there is no evidence (or which are, in fact, contradicted by the evidence). Optimists — which can be defined as people who disregard some of the negative facts about their own abilities or the state of the world — apparently live longer and happier lives than pessimists (who actually tend to be realists, i.e., they come closer to aligning their beliefs to the available evidence). So from the point of view of practical reason, it may be argued that it is actually rational for people not to behave too strictly as Bayesian estimators, theoria be damned.

The upshot is that we skeptics are perfectly justified in telling someone who believes in, say, astrology, that he is theoretically irrational, but not necessarily instrumentally so. Then again, things get complicated by the fact that if the person in question starts acting on the basis of his false beliefs in situations where his health is at risk (say, by going for homeopathic “remedies” instead of proven medical procedures) then we can justifiably say that he is behaving irrationally both from the point of view of theoria and of praxis — at least assuming that he actually values his life over his temporary psychological satisfaction.

So, the next time you are about to hurl the “that’s irrational” judgment at someone, stop and think in what sense you mean it, and consider whether it actually applies to the situation at hand. It may save you some grief and frustration, and who knows, you may even get your point of view across in a less threatening manner. Assuming that’s of concern to you, of course.