Rationality, rationalism, and alternatives

This chapter defines some key terms of In the Cells of the Eggplant: rationality, rationalism, reasonableness, and meta-rationality.


Meanings of “rational” have multiplied and evolved over centuries, which can create confusion. In the broadest sense, it’s synonymous with “sensible.” In some narrow senses, it means using one specific mathematical system to decide what to do.

I will use it in an intermediate sense: rational methods are formal, systematic, explicit, technical, abstract, atypical, non-obvious ways of thinking and acting, which have some distinctive virtue relative to informal ones.1 “Methods” suggests that rationality is a practical activity: things we actually do, rather than a metaphysical ideal we should aspire to.

“Systematic” and “formal” are key criteria, but both are nebulous. They are a matter of degree. Mathematical logic is extremely formal; a chemistry methods manual is quite formal; a corporate personnel policy is somewhat formal; a “Do Today” task checklist is only barely formal. “System” is used vaguely to mean almost anything complicated. I’ll use it a little more specifically, as meaning a set of rules that can be printed in a book, which a person can consciously follow, and the activities and mechanisms that result.

Rationality works mainly with general knowledge. Ideally, it aims for universal truths. Typically, knowledge of a specific object does not count as “rational” unless it applies to every other object in some class. The glory of Newton’s theory of gravity is that it is true uniformly everywhere in the universe, equally for an apple and an asteroid.2 In fact, we’ll see that formal systems cannot deal with particular physical objects at all—one reason rationality is inadequate by itself.


I will use rationalism to mean any belief system that makes exaggerated claims about the value of rationality, going beyond the evidence of common experience. In the plural, rationalisms are diverse belief systems of this sort.

The most influential rationalisms attempt universality across domains: they are meant to apply in all situations and task types. Others are more specific: particular notions of rationality that apply only in mathematics, science, law, management, or accounting. The Eggplant considers mainly universal rationalisms, or ones meant to apply broadly in technical fields.

Typically, rationalisms attempt to form rational theories of rationality. That is, they seek systematic, explicit, technical, abstract, non-obvious explanations for how and why rationality works. Ideally, they aim for definite proof of rationality’s universal efficacy.

Typically, rationalisms specify some ultimate criterion according to which thinking or acting could be judged to be correct or optimal. Typically, rationalisms say that thinking in accordance with the criterion leads to true beliefs. They may also claim rationality yields maximally effective action.

For rationalism, ideal rationality means conforming to the criterion. Rationalism is normative: everyone ought to think and act that way, as nearly as possible. Rationality, according to most rationalisms, is fully adequate on its own.

Under this definition, “rationalism” must go beyond “formal methods are often useful, hooray!” That is the common experience: for anyone who uses such methods, their value is obvious.3 I will use rationalist to mean someone who promotes rationalism—rather than someone who just finds methods of systematic rationality often useful in practice.

Let’s consider a variety of claims about rationality, roughly from weaker to stronger:

  1. It is better to be rational than irrational
  2. Systematic rationality often works, so you should use it when appropriate
  3. Rationality (whose definition is left vague) is always good
  4. Rationality is all there is to thinking and acting well; it is sufficient for all purposes, and there’s nothing else you need
  5. Rationality is defined by such-and-such a criterion; you should conform to it as nearly as you can
  6. Certain specified methods meet the rationality criterion, so you should use them whenever you can
  7. There’s a single master method of rationality, which guarantees an optimal result

I think claims 1 and 2 are correct: formal rationality is hugely valuable and you should use it often. I will not count this as “rationalism.” Not everyone agrees, though. Let’s say that anti-rationalism is any worked-out denial of either 1 or 2. Meta-rationalism—the understanding presented in this book—is not anti-rationalism, since it affirms the value of rationality.

“Rationalism” might be defined as holding claim 4 (that rationality is always sufficient) or above. Meta-rationalism denies 4-7, so it is not rationalism.

Claim 3 is a vague attitude of alignment. If rationality means just “thinking and acting well,” then it is correct by definition. Also, claim 3 is importantly right if it’s just a rejection of anti-rationalism. On the other hand, a diffuse, incoherent rationalist faith is imparted implicitly in the science curriculum. There must be a correct way to think, some rationalists suggest, but we don’t know quite what it is; or they extol a vague principle like “the scientific method.” No one has been able to give a detailed, empirically adequate explanation of what “the scientific method” is, so advocating it is nearly vacuous.4

I think the stronger claims 4-7 are mistaken. Formal rationality is rarely if ever sufficient on its own in real-world situations; there’s no fixed criterion for rationality; nothing can be guaranteed by or about rationality in practice; and there is no method that is always rational to use.

Universal rationalisms are usually based on some bit of mathematics. They point out that the math is incontrovertibly correct, and base their supposed guarantees on that certainty. But rationality is not just solving mathematical puzzles; it is using that math in the real world, whose nebulosity makes guarantees impossible.

Distinguishing weaker and stronger claims about rationality may help correct both rationalist and anti-rationalist errors. I suspect many anti-rationalists react to overstated rationalist claims, rightly rejecting them, but then mistakenly go on to deny that systematic rationality is often valuable. I suspect many rationalists rightly wish to defend rationality’s genuine value, but mistakenly go on to affirm implausibly strong claims as well. Rationality does have “distinctive virtues” (which we’ll return to in Part Three); but these are nebulous and cannot be guaranteed.

Rationalism and nebulosity

Part One explains a series of specific technical difficulties rationalism encounters. Each failure mode has the same underlying cause: denial of nebulosity.5

The problem with rationalism is not that it is false as an abstract philosophical theory. (Who cares?) The problem is that it is misleading in practice. It encourages you to overlook nebulosity, so you end up using rationality wrongly. This is not a minor or theoretical danger. The replication crisis has revealed that most supposed knowledge in many scientific fields, derived through misuse of rational methods, is false.

Rationalism is based on a fantasy of how we would like knowledge, action, and reality to work. It would be highly convenient if they did. In a world without nebulosity, in which objects and properties were perfectly crisp, rationality would be fully adequate. But we do not live in such a world. To the extent that rationality does work, it is largely because we have engineered our world to make it behave more nearly that way.

Non-rational, merely reasonable judgement is unreliable, sometimes uncomfortable, and leads to conflict when people get different answers. When they get stubborn about that, or when misjudgment leads to disaster, it’s easy to regard all “reasonableness” as simply irrational. The hope of rationalism is that some mechanical criterion or procedure could provide certainty, understanding, and control by eliminating non-rational factors. This is not possible, because rationality by itself can’t deal with the nebulous eggplant-sized world at all. Abstract, formal reasoning cannot reach into that realm; it requires reasonable activity as a bridge.


But Poetry! But Love! But Dreams!

Familiar rejections of rationalism fault it for neglecting aesthetics, emotions, consciousness, morality, spirituality, and so on. Philosophers call this the Romantic critique.

The Eggplant doesn’t address any of that at all. It doesn’t make that sort of argument. It neither agrees nor disagrees with Romanticism.

Instead, Part One explains how rationalism fails technically, on its own ground, in its own terms. Part Three gives a better explanation of rationality, again without addressing aesthetics, emotions, and so on. Those domains are important in other ways, and do have some bearing on the use of rationality, but they are incidental to the concerns of this book.


In everyday usage, “rational” has an informal meaning of “thinking and acting in ways that make sense and are likely to work.” In this sense, “rational” is synonymous with “sensible.” It means “not stupid, crazy, or meaningless.” I will call this reasonableness, reserving “rationality” for systematic methods.6

Much of The Eggplant is about the relationship between these two. Understanding that relationship is a prerequisite for meta-rationality. Rationalism misunderstands reasonableness as a primitive approximation to rationality. In fact, it has somewhat different—though overlapping—functions. “Mere” reasonableness addresses the nebulosity of the everyday world effectively, which formal rationality can’t. Meta-rationality combines resources from reasonableness and rationality, plus ones of its own, to understand and act effectively in circumstances the others cannot manage.

I’ll use irrational to mean failure or refusal to think well or act effectively when you should. It means “unreasonable” or “nonsensical,” or “stupid” or “crazy,” in the non-clinical sense of those words. By this definition, irrationality is contrary to all three of reasonableness, rationality, and meta-rationality. I will not use it to mean “not systematically rational.”

Meta-rationality and meta-rationalism

Meta-rationality means figuring out how to apply reasonableness and rationality in a specific situation, and skill in doing so. It is a word I made up, to cover insights about the use of rationality gathered from many disparate fields.7

Rationality and meta-rationality are complementary activities. Meta-rationality is not an alternative to rationality. Neither can operate without the other; they walk hand-in-hand.

Meta-rationality is not in the business of finding true beliefs or optimal actions. That’s rationality’s job. On the other hand, getting good at meta-rationality will make you more effective at rationality, and therefore better at finding true beliefs and optimal actions.

Meta-rationality selects and adapts rational methods to circumstances, so it is meaningless without rationality. Conversely, you cannot apply rationality without making meta-rational choices. However, since meta-rationality is rarely taught explicitly, it’s common to use only the simplest, default meta-rational criteria. Those are meta-rational nonetheless: there is no universal rational method, so in any situation you have to choose one and figure out how to apply it.

We’ll see that rationality cannot be applied to concrete problems without bringing in reasonableness as well. Meta-rationality usually involves understanding, and sometimes altering, the relationships between reasonableness and rationality in particular circumstances.

Meta-rationality is not the application of formal rationality to itself (as one might suppose from its name). Applying rationality to itself is a rationalist program. We’ll see that, because of nebulosity, reasoning about how to apply rationality cannot be formally rational. (But it should not be irrational or anti-rational either!)

Meta-rationalism is an understanding of how and when and why reasonableness, rationality, and meta-rationality work. Whereas rationality and meta-rationality are different sorts of things, rationalism and meta-rationalism are the same sort of thing: explanations of effective thought and action. Meta-rationalism finds rationalism an inadequate account, and offers a complete replacement.8 So, perhaps confusingly, while rationality and meta-rationality are complementary activities, rationalism and meta-rationalism are incompatible explanations.

Once you recognize that denial of nebulosity is the deep structure underlying each of the difficulties rationalism encounters, the solution approach is obvious: accept nebulosity from the beginning, and work with it, instead of trying to ignore or eliminate it. As a practice, meta-rationality does just that. As a theory, meta-rationalism is a more accurate account of the sort of world we live in; and so it gives better advice than rationalism in cases in which nebulosity matters.

  1. 1.Some non-rational systematic religions and philosophies would also meet these criteria. There is a “demarcation problem” here. The usual meaning of “the demarcation problem” is to find a test that clearly distinguishes science from non-science. This seems to be impossible. Different sciences work quite differently, and have no single well-defined feature in common. However, the demarcation problems for both science and rationality are rarely an issue in practice. We know science and rationality when we see them, and can usually make a cogent argument for why a particular method or system is scientific or rational or not, even if there is no general rule.
  2. 2.This applies to semi-formal rational systems as well. A company policy that said “employees must turn in their weekly timesheets by the following Thursday, except Bertrand” would not count as rational. In a rational policy, if Bertrand is an exception, it must be as an instance of a class. For example, if Bertrand is an exception because he’s on a secret solo dogsled expedition to the South Pole, a rational policy would be “employees must turn in their timesheets by the following Thursday, unless they are out of internet range, in which case they must turn it in by the Thursday following their return to civilization.”
  3. 3.In “Ignorant, irrelevant, and inscrutable,” I discuss irrationalists who simply don’t understand that formal methods are often useful, and anti-rationalists who oppose systematic rationality for aesthetic, political, religious, or “spiritual” reasons. Since the European Enlightenment, anti-rationalism has mainly been suppressed in favor of a consensus in favor of rationality among the powerful. There are ominous signs that this consensus is now failing. See “A bridge to meta-rationality vs. civilizational collapse.”
  4. 4.This is the demarcation problem again. It seems that any set of criteria for what counts as scientific winds up excluding some things that most scientists agree are science, and/or including some thing that aren’t. False positives typically include “pseudoscience,” meaning work that presents itself as science, and meets most or all typical criteria, but is clearly bogus.
  5. 5.In the language of Meaningness, this is a form of eternalism. Equivalently, it is the fixation of patterns as ontological absolutes. I mostly don’t use these terms in The Eggplant.
  6. 6.Although the concept is familiar to everyone, there seemed to be no standard academic term for “reasonableness” when I began writing about it in 2017. Interestingly, a 2020 paper found that lay people recognize the distinction, and do use the words “reasonable” and “rational” for it. Igor Grossman et al., “Folk standards of sound judgment: Rationality Versus Reasonableness,” Science Advances 8 January 2020.
  7. 7.A few people have used the term “meta-rationality” with similar meanings before, in passing, but I don’t know of any previous detailed account. The most extensive previous use I’ve found is in Chapter 6 of Keith Stanovich’s Decision Making and Rationality in the Modern World. He uses the term to mean reflection on one’s preferences and on the consequences of choices in a decision-theoretic framework. This use is compatible with mine, although a narrower conception, and not elaborated in much detail.
  8. 8.Logically, there could be multiple meta-rationalisms: different theories about the relationships among reasonableness, rationality, and meta-rationality. Currently, there is not even one fully worked-out version, so meta-rationalisms in the plural are only hypothetical.