Introducing key terms

Cirrus clouds

Exactly how many clouds are in this photograph?
Image courtesy Dimitry B

This section explains how The Eggplant uses these words: nebulosity; ontology and epistemology; rationality, rationalism and anti-rationalism; reasonableness and irrationality; meta-rationality and meta-rationalism.

It also sketches the ways these concepts relate to each other. That gives, in effect, another introductory summary of some major themes of the book.


Literally, nebulosity means “cloud-like-ness”:

  • Boundaries: Clouds do not have sharp edges; they thin out gradually at the margin. As you approach a cloud (in an aircraft, or on a mountain hike), you cannot say quite when you have entered it.
  • Identity: It may be impossible to say where one cloud ends and another begins; whether two bits of cloud are part of the same whole or not; or to count the number of clouds in a section of the sky.
  • Categories: Cirrocumulus shades into cirrus and into altocumulus; clouds of intermediate form cannot meaningfully be assigned to one or another.
  • Properties: Depending on temperature and density, clouds may be white, gray, blue, or irridescent. There are no specific dividing lines between these colors. Clouds have diverse, highly structured shapes, which cannot be precisely described. First, because the edges are vague; and second because the shape is so complex that a full description would be overwhelmingly gigantic even were it possible. Yet meteorologists find useful phrases like “ragged sheets,” “wavy filaments,” “bubbling protuberances,” or “castle-like turrets.”

Clouds are an extreme case, but nebulosity is pervasive. Other than in mathematics and fundamental physics, nothing is ever definitely this-or-that. Everything is always somewhat this and somewhat that. Put under high enough magnification, a stainless steel ball exhibits the same indefiniteness as a cloud. No ball can be perfectly round, nor made of perfectly pure steel, nor can one definitely say that some particular atoms are part of it or part of its surrounds.

For this reason, there are few if any absolute truths about the eggplant-sized world. Mostly, the best we can ever get is “true for all practical purposes.” And most of the truths we use, even in the hard sciences, are “pretty much true” or “true as far as a particular use goes.” This raises occasional problems for rationality in practice, and causes serious difficulties for rationalism as a theory. Meta-rationalism addresses these issues effectively.

Because of nebulosity, definitions can’t be perfectly precise. Some categories hang together only by “family resemblance”: there is no single common feature, it’s just that this is similar to that, which is similar to another thing.1

However, it’s often useful to sharpen categories somewhat, and to disambiguate word meanings to some extent. Several of the key terms in The Eggplant—especially “rationality”—have previously been used in multiple ways, and clarity requires pointing out which I intend. The definitions in this section will still be somewhat vague. Meanings will come into better focus gradually, through understanding words’ use in later discussions.

“Nebulosity” is itself, necessarily, a nebulous concept, which cannot be precisely defined. However, since it is so central to The Eggplant, I’ll explain it in more detail in a whole section after this one.

Ontological and epistemological

The Eggplant isn’t a philosophy book, so it uses “ontological” as engineers do.2 Ontology is about how the world is. The ontological questions are: “What things, of what sorts, are there? What properties and relationships do they have?” By an ontology, engineers mean a set of answers, usually relative only to a specific domain.

Rather than advocating a particular ontology, I will reply, over and over again, in different ways: “These questions have no definite answers, due to nebulosity.” Meta-rationality is concerned mainly with ontological questions, and gives nebulous—but useful—answers.

Epistemology is about what we know of the world. The epistemological questions are: “What is knowledge? What is a belief? How can we get true beliefs and eliminate false ones?” Rationality is mainly concerned with these epistemological issues; it generally ignores ontological ones.

We can’t fully separate epistemology and ontology. The first part of this book shows how rationalism tries to do that, and so goes wrong. How things are partially determines how you can know them. Nebulosity is pervasive, so little could be known definitely, even if we had unlimited access to reality. Most facts about clouds and eggplants are not absolutely true, only true-enough, and so they cannot accurately be believed absolutely. Meta-rational epistemology takes this nebulosity of truth, knowledge, and belief into account.


Meanings of “rational” have evolved and proliferated over centuries. These share only a family resemblance, so no precise definition is possible. Various schools of thought have refined and promoted particular versions. Part I of The Eggplant explores some specifically.

I will treat rationality as a practical activity, things we actually do, rather than as a metaphysical ideal we should aspire to. Generally, 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.3

“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.

Rationality works mainly with general knowledge. Ideally, it aims for universal truths. Generally, 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.4 In fact, we’ll see that formal systems cannot deal with particular physical objects at all—one reason rationality is inadequate by itself.

Reasonableness and irrationality

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.” Somewhat arbitrarily, I will call this reasonableness, and reserve “rationality” for systematic methods.5

Much of The Eggplant is about the relationship between these two. Understanding that is a prerequsite 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 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.”

Rationalism and anti-rationalism

I will use rationalism to mean any belief system extolling broad claims about 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, they say that thinking in accordance with the criterion reliably produces 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.

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.6 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. I will not count them as “rationalism.” Not everyone agrees with them, though. Let’s say anti-rationalism is any worked-out denial of either 1 or 2. Meta-rationalism is not anti-rationalism, since it affirms both. “Rationalism” might be defined as holding claim 4 or above. Meta-rationalism denies 4-7, so it is not rationalism.

Claim 3 is a diffuse 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 STEM 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.

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.

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 III); but these are nebulous and cannot be guaranteed.

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, 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.

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, and the bridging function of reasonableness it demands; 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.

Part I of The Eggplant explains a series of specific technical difficulties rationalism encounters. Each failure mode has the same underlying cause: denial of nebulosity.7

Meta-rationality and meta-rationalism

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

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.

Meta-rationality is not the application of formal rationality to itself (as one might suppose from its name).8 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: accounts of effective thought and action. Meta-rationalism finds rationalism an inadequate account, and offers a complete replacement.9 So, perhaps confusingly, while rationality and meta-rationality are complementary activities, rationalism and meta-rationalism are incompatible theories.

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.

Meta-systematicity is a broader category that includes meta-rationality. It is reflection on how systems, not necessarily formally rational ones, relate to their circumstances. One may take a meta-systematic approach to psychological, social, and cultural systems. These possibilities are explored elsewhere in Meaningness, the work of which The Eggplant is a part.10

  • 1. The understanding of categories in terms of “family resemblance” originates with Ludwig Wittgenstein’s Philosophical Investigations.
  • 2. Some of the questions I describe as “ontological” might rather be called “metaphysical” by philosophers. The distinction between ontology and metaphysics is nebulous, however. I’m mostly avoiding “metaphysics” because for many people it means “holistic chakra-balancing aromatherapy.” On the other hand, ontology, as a branch of academic philosophy, examines many issues that are out of this book’s scope.
  • 3. 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 criteria that clearly distinguish science from non-science. This seems to be impossible. Different sciences seem to bear only a family resemblance to each other, with no single 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.
  • 4. 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.”
  • 5. Although the concept is familiar to everyone, there seems to be no standard word for what I’m calling “reasonableness.” That is probably because it is usually viewed as a half-baked approximation to rationality, and therefore can be ignored. As we will see, this is inaccurate.
  • 6. In “Ignorant, irrelevant, and inscrutable,” I discuss the irrationalists who simply don’t understand that formal methods are often useful, and the 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 may now be failing. See “A bridge to meta-rationality vs. civilizational collapse.”
  • 7. 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.
  • 8. To avoid this possible confusion, a better term might be “circumrationality.” It’s about the circumstances that surround the application of rationality. That sounds cumbrous, though. I don’t much like any of the alternative terms I’ve considered.
  • 9. 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.
  • 10. Meta-rationality and meta-rationalism are both also types of metacognition, another related term used mainly in education theory. It means knowledge of, and skill in using, one’s own cognitive capacities. It’s a much broader category, not focussed on formal rationality, and I won’t refer to it again in this book.


This page is in the section Introduction: Because rationality matters,
      which is in In the cells of the eggplant,
      which is in ⚒ Fluid understanding: meta-rationality,
      which is in ⚒ Sailing the seas of meaningness,
      which is in Meaningness and Time: past, present, future.

The next page in this section is The function and structure of the eggplant.

This page’s topic is Rationalism.

General explanation: Meaningness is a hypertext book (in progress), plus a “metablog” that comments on it. The book begins with an appetizer. Alternatively, you might like to look at its table of contents, or some other starting points. Classification of pages by topics supplements the book and metablog structures. Terms with dotted underlining (example: meaningness) show a definition if you click on them. Pages marked with ⚒ are still under construction. Copyright ©2010–2020 David Chapman. Some links are part of Amazon Affiliate Program.