About Rationally Speaking

Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Monday, January 31, 2011

Are Intuitions Good Evidence?

by Julia Galef
In Episode 16 of the Rationally Speaking podcast, Massimo said that despite some disagreements over particular philosophical issues, there is at least a consensus within the field about the rules of how to argue. I agree to a large extent. Philosophers more or less all concur about the rules of deductive logic and what constitutes a formal logical fallacy, as Massimo rightly pointed out. That’s not to say that no one ever makes a mistake, of course, but they do share standards of argumentation towards which they all strive. That commitment to rigorous thought is why I tend to love talking to philosophers, and it’s why I’ve ended up with an amusingly philosopher-heavy friend group.
Most philosophical arguments, however, occur not in the neat and orderly garden of formal logic, but in the wilderness outside its walls. Which means that the consensus on “how to argue” can get a little fuzzy. In particular, there’s one interesting controversy about philosophical methodology that I mentioned during the show but didn’t have time to elaborate on1: Is it legitimate to cite one’s intuitions as evidence in a philosophical argument?
It’s an important question, because appeals to intuitions are ubiquitous in philosophy. What are intuitions? Well, that’s part of the controversy, but most philosophers view them as intellectual “seemings.” George Bealer, perhaps the most prominent defender of intuitions-as-evidence, writes, “For you to have an intuition that A is just for it to seem to you that A… Of course, this kind of seeming is intellectual, not sensory or introspective (or imaginative).”2 Other philosophers have characterized them as “noninferential belief due neither to perception nor introspection”3 or alternatively as “applications of our ordinary capacities for judgment.”4

Philosophers may not agree on what, exactly, intuition is, but that doesn’t stop them from using it. “Intuitions often play the role that observation does in science – they are data that must be explained, confirmers or the falsifiers of theories,” Brian Talbot says.5 Typically, the way this works is that a philosopher challenges a theory by applying it to a real or hypothetical case and showing that it yields a result which offends his intuitions (and, he presumes, his readers’ as well).
For example, John Searle famously appealed to intuition to challenge the notion that a computer could ever understand language:
“Imagine a native English speaker who knows no Chinese locked in a room full of boxes of Chinese symbols (a data base) together with a book of instructions for manipulating the symbols (the program). Imagine that people outside the room send in other Chinese symbols which, unknown to the person in the room, are questions in Chinese (the input). And imagine that by following the instructions in the program the man in the room is able to pass out Chinese symbols which are correct answers to the questions (the output)… If the man in the room does not understand Chinese on the basis of implementing the appropriate program for understanding Chinese then neither does any other digital computer solely on that basis because no computer, qua computer, has anything the man does not have.”
Should we take Searle’s intuition that such a system would not constitute “understanding” as good evidence that it would not? Many critics of the Chinese Room argument argue that there is no reason to expect our intuitions about intelligence and understanding to be reliable.
Ethics leans especially heavily on appeals to intuition, with a whole school of ethicists (“intuitionists”) maintaining that a person can see the truth of general ethical principles not through reason, but because he “just sees without argument that they are and must be true.”6 Intuitions are also called upon to rebut ethical theories such as utilitarianism: maximizing overall utility would require you to kill one innocent person if, in so doing, you could harvest her organs and save five people in need of transplants. Such a conclusion is taken as a reductio ad absurdum, requiring utilitarianism to be either abandoned or radically revised – not because the conclusion is logically wrong, but because it strikes nearly everyone as intuitively wrong.
British philosopher G.E. Moore used intuition to argue that the existence of beauty is good irrespective of whether anyone ever gets to see and enjoy that beauty. Imagine two planets, he said, one full of stunning natural wonders – trees, sunsets, rivers, and so on – and the other full of filth. Now suppose that nobody will ever have the opportunity to glimpse either of those two worlds. Moore concluded, “Well, even so, supposing them quite apart from any possible contemplation by human beings; still, is it irrational to hold that it is better that the beautiful world should exist than the one which is ugly? Would it not be well, in any case, to do what we could to produce it rather than the other? Certainly I cannot help thinking that it would."7
Although similar appeals to intuition can be found throughout all the philosophical subfields, their validity as evidence has come under increasing scrutiny over the last two decades, from philosophers such as Hilary Kornblith, Robert Cummins, Stephen Stich, Jonathan Weinberg, and Jaakko Hintikka (links go to representative papers from each philosopher on this issue). The severity of their criticisms vary from Weinberg’s warning that “We simply do not know enough about how intuitions work,” to Cummins’ wholesale rejection of philosophical intuition as “epistemologically useless.”
One central concern for the critics is that a single question can inspire totally different, and mutually contradictory, intuitions in different people. Personally, I’ve often been amazed at how completely I disagree with what a philosopher claims is “intuitively” the case. For example, I disagree with Moore’s intuition that it would be better for a beautiful planet to exist than an ugly one even if there were no one around to see it. I can’t understand what the words “better” and “worse,” let alone “beautiful” and “ugly,” could possibly mean outside the domain of the experiences of conscious beings. I know I’m not alone in my disagreement with Moore, yet I’ve also talked to other well-respected professional philosophers who claim to share his intuition.
It’s common, in fact, for philosophers’ intuitions to diverge. If we want to take philosophers’ intuitions as reason to believe a proposition, then the existence of opposing intuitions leaves us in the uncomfortable position of having reason to believe both a proposition and its opposite. “We all know from even casual philosophical discussion that philosophers don’t always share one another’s intuitions,” Rutgers’ Alvin Goldman writes. Just to pick one of myriad examples, here is the eminent Hilary Putnam reacting to David Lewis’ appeals to metaphysical intuitions: “[F]ar from sharing these intuitions, I feel that I don’t even understand what they mean,” he complained.8 And Cummins and Weinberg both propose that the degree of disagreement on intuition may be understated by selection bias. “I suspect there is overall less agreement than standard philosophical practice presupposes, because having the ‘right’ intuitions is the entry ticket to various subareas of philosophy,” Weinberg says.
But the problem that intuitions are often not universally shared is overshadowed by another problem: even if an intuition is universally shared, that doesn’t mean it’s accurate. For in fact there are many universal intuitions that are demonstrably false. Consider our intuitive notions about math. It seems intuitively obvious that there must be more rational numbers than positive integers – because, after all, there are an infinite number of rational numbers between any two positive integers. Yet we can prove that set of rational numbers is the same size as the set of positive integers.
Our naïve beliefs about physics are no better. People who have not been taught otherwise typically assume that an object dropped out of a moving plane will fall straight down to earth, at exactly the same latitude and longitude from which it was dropped. What will actually happen is that, because the object begins its fall with the same forward momentum it had while it was on the plane, it will continue to travel forward, tracing out a curve as it falls and not a straight line. “Considering the inadequacies of ordinary physical intuitions, it is natural to wonder whether ordinary moral intuitions might be similarly inadequate,” Princeton’s Gilbert Harman has argued,9 and the same could be said for our intuitions about consciousness, metaphysics, and so on.
We can’t usually “check” the truth of our philosophical intuitions externally, with an experiment or a proof, the way we can in physics or math. But it’s not clear why we should expect intuitions to be true. If we have an innate tendency towards certain intuitive beliefs, it’s likely because they were useful to our ancestors. But there’s no reason to expect that the intuitions which were true in the world of our ancestors would also be true in other, unfamiliar contexts, such as objects being dropped from airplanes. (Or the emergence of consciousness from a complex system of unconscious components.)
And for some useful intuitions, such as moral ones, “truth” may have been beside the point. It’s not hard to see how moral intuitions in favor of fairness and generosity would have been crucial to the survival of our ancestors’ tribes, as would the intuition to condemn tribe members who betrayed those reciprocal norms. If we can account for the presence of these moral intuitions by the fact that they were useful, is there any reason left to hypothesize that they are also “true”? The same question could be asked of the moral intuitions which Jonathan Haidt has classified as “purity-based” – an aversion to incest, for example, would clearly have been beneficial to our ancestors. Since that fact alone suffices to explain the (widespread) presence of the “incest is morally wrong” intuition, why should we take that intuition as evidence that “incest is morally wrong” is true?
The still-young debate over intuition will likely continue to rage, especially since it’s intertwined with a rapidly growing body of cognitive and social psychological research examining where our intuitions come from and how they vary across time and place. I’ll be following it with interest – as a metaphilosophical question, its resolution bears on the work of literally every field of analytic philosophy, except perhaps logic. Can analytic philosophy survive without intuition? (If so, what would it look like?) And can the debate over the legitimacy of appeals to intuition be resolved with an appeal to intuition?

[Note: Massimo will publish a response to this friendly attack in a couple of days, as soon as he has figured out what his intuitions about Julia's arguments are.]
[Julia's Note: This was certainly meant as friendly, but not as an attack! I'm just explaining an interesting controversy in the field.]

(1) My disagreement with Massimo in the show begins around 20:30 and seems, in retrospect, to be primarily due to my characterization of appeals to intuition as a “rule of inference” among philosophers. Massimo (I believe) took “rule of inference” to refer to a formal rule of deduction, and replied that philosophers do not disagree about formal logic, whereas I was using “rule of inference” to mean, basically, “philosophical methodology.”
(2) George Bealer (1996).
A priori knowledge and the scope of philosophy.
(3) Sosa, E. (1998). ‘Minimal Intuition’, in M. De Paul and W. Ramsey (eds.), Rethinking Intuition, Lanham, MD: Rowman and Littlefield.

(4) Timothy Williamson (2004).
Philosphical 'Intuitions' and Scepticism About Judgement.
(5) Talbot, Brian (2009).
How to Use Intuitions in Philosophy.
(6) Harrison, J. (1967). “Ethical Objectivism,” In P. Edwards (Ed.), The Encyclopedia of Philosophy (Vols. 3-4, pp. 71-75).

(7) Moore, G. E. (1903).
Principia Ethica.
(8) Putnam, Hilary (1995).
Renewing Philosophy.
(9) Harman, G. (1999). “Moral Philosophy Meets Social Psychology: Virtue Ethics and the fundamental Attribution Error,” Proceedings of the Aristotelian Society (New Series), 119: 316–31.


  1. Many debates on this rest on misunderstanding and imprecise definitions. For instance, Searle's man in the Chinese room does not "understand" the Chinese language in the usual sense of the word (understanding it instantly upon reading or hearing, without the aid of props like a dictionary), but (1) he "understands" Chinese in the sense of "being able to respond to questions", and (2) the Chinese is not evidence of "understanding" in the intuitive sense, but of the capacity to respond to questions like in a Turing machine and just as the Turing machine does not prove that the computer is "intelligent" in the intuitive sense. The point of the room (Turing or Chinese) is showing that an external observer of questions and answers cannot distinguish between a human and a machine, or between a native Chinese and the Man-in-the-Room with his symbols and program. If one uses the correct concepts for those situations the Searle's argument becomes pointless.

    Another confusion is between intuition as evidence (which it is not) and intuition as rule for fast decisions (which it is very good at, as shown for instance by Gerd Gigerenzer's experiments in bounded rationality (cf refs).

    Gigerenzer, Gerd et al, 1999. Simple Heuristics that make us Smart (OUP)
    Gigerenzer, Gerd 2007. Gut feelings: The intelligence of the inconscious (Viking)
    Gigerenzer, Gerd 2000. Adaptive Thinking: Rationality in the Real World (OUP)
    Gigerenzer, Gerd and Reinhard Selten (eds)2002. Bounded Rationality: The Adaptive Toolkit (MIT Press).

  2. A bit of personal experience: having studied for years the analytic philosophy of social sciences, I have developed the intuition that many intuitions many authors have come from the protestant origins of their cultures, and for mediterranean and catholic people like me sound simply absurd (like, e.g., the 'intuition' that cooperation in a prisonner's dilemma is morally desirable, or that communities are intrinsically good).

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  5. Whew, good point. I was involved in an argument the other day over the same point. "Intuition" or "gut feelings" may be fine, whatever they are but can lead down some messy roads to extremely subjective conclusions.
    I will be checking out all of those above references and may check in later as I have an intuitive feeling that I may wish to comment further.

  6. "If we have an innate tendency towards certain intuitive beliefs, it’s likely because they were useful to our ancestors."

    Indeed, from this it seems reasonable to hypothesize that intuition could be a vestigial form of intelligence, useful and correct to our ancestors.

    "But there’s no reason to expect that the intuitions which were true in the world of our ancestors would also be true in other, unfamiliar contexts, such as objects being dropped from airplanes."

    I would suggest our evolving analytical mind has not caught up with our impulse driven creative mind. We can invent astounding technologies and compose symphonies without fully understanding what we've done, even if how we've done it comes easily.

    Given this, intuition should still be considered "legitimate," used and engaged at least to move beyond it.

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  8. This has inspired me to more concisely reformulate my objection regarding free will; I find it difficult to productively discuss it (or even understand the meaning of the term), because people are appealing to intuitions about the nature of choice that I don't share and thus have to go to some pains to unpack.

  9. "But the problem that intuitions are often not universally shared is overshadowed by another problem: even if an intuition is universally shared, that doesn’t mean it’s accurate. For in fact there are many universal intuitions that are demonstrably false."

    I think that there's also a problem when one's intuitive concepts aren't quite nuanced enough to get at what one really means. For example, if one looks at the interval [0,1], there would seem to be more rational numbers than numbers in a Cantor set (at least, that's the intuition I first had, since the Cantor set had so many finite-size "holes" in it, whereas the rational numbers have no such holes). In reality, the Cantor set is uncountable and therefore larger. However, the intuition that there are more rational numbers is born out in a different way; the rational numbers are dense over the entire interval, whereas the Cantor set is dense nowhere. The precisely defined notion of density turns out to be part of a toolbox to replace (or at least further specify) the vaguer intuitive notions of "how many" or "how much" of something is present. Those intuitions turn out to have some merit but are generally misleading.

  10. Thanks for this. One of my favorite topics.

  11. "maximizing overall utility would require you to kill one innocent person if, in so doing, you could harvest her organs and save five people in need of transplants."

    Yes that works for machines who are programmed to maximize utility, but human beings are not machines and operate under rather different constraints. Human beings are signatories to the Social Contract and that contract says 'don't hurt each other' it does not say (or says in a much weaker clause) 'heal each other'. Hurting requires abilities each of us possess and is accomplished with readily available materials (like guns for instance). It can even be accomplished by sheer accident whereas healing generally requires special equipment and special training. Every one of us is a potential harmer, few of us are potential healers. Killing someone to harvest their organs to save five people weighs the very strong prohibition against harm against the very weak imperative to heal which is why it seems intuitively wrong. Unless you are a machine of course.

  12. Excellent article! The definitions you gave of intuition were rather odd. I tend to see intuitions as either (a) evolutionarily adaptive rules of thumb, or (b) results of subconscious but non-mysterious reasoning procedures. As such, my attitude to them is positive but extremely cautious.

    Incidentally, Moore's "beautiful planet" argument is hilarious.

  13. "Incidentally, Moore's 'beautiful planet' argument is hilarious."

    Welcome to 70% of 20th century analytic philosophy. :(

    Still, at least it's not continental philosophy! :)

  14. Thanks for the feedback, everyone. I should mention that I do think the line between (self-evident) reasoning and (ungrounded) intuition is a very fuzzy one. Certainly I don't mean to imply that every claim which isn't either (1) empirical or (2) provable mathematically is baseless. The tricky part (and a large part of the intuitions debate) is figuring out which seemingly "self-evident" claims should in fact be taken as such. (Though I'd say the existence of a large disagreement over whether a claim is "self-evidently" true or false is probably a bad sign.)

    Also, for anyone looking to read a longer overview of this issue, with examples of pro-intuitions papers, check out this syllabus: http://jonathanichikawa.net/papers/intuitions-bib.pdf
    ... I also like this paper by Goldman, who is a moderate intuitions-proponent: http://philpapers.org/rec/GOLPIT-2

  15. Excellent post, Julia.

    "Intuition" is a tricky word with a range of meanings, but I think what we mean by it in this context is basically a belief for which we cannot give a decent argument.

    Note that many of our reasonable beliefs have not been justified by arguments. When I look out of the window and see a squirrel in the garden, subconscious processes cause me to believe that there's a squirrel in the garden. I don't need to construct an argument before I believe it. And in most cases I don't even subject the belief to conscious rational scrutiny after it's formed. But that doesn't mean that it's irrational for me to believe it.

    Not only is intuition a rational type of belief but intuitions can rationally be taken as evidence in support of claims. If people report to me their belief that there's a squirrel in the garden, then I have evidence that there is a squirrel in the garden, even if their belief was intuitive and unexamined. I can use that evidence in an argument for the existence of the squirrel.

    However, when it comes to more significant and difficult questions (such as the major questions of science and philosophy) experience has taught us that intuition is a poor guide to truth. It may be evidence, but it's very poor evidence.

    In my view, the answers to most of the major questions of philosophy are deeply counterintuitive, and the failure of many philosphers to challenge their intuitions strongly enough is a significant contributory factor in the relative lack of progress that philosophy has made. The nature of consciousness is one of the most conceptually challenging questions of all, and it's absurd to try to settle it by a brute appeal to intuition.

  16. P.S. I'd like to add something.

    Inductive inferences can never be supported by a complete argument, in the sense of an argument that takes us by unimpeachable logical steps from premises to conclusion. (That would be a deductive argument.) They always involve a larger or smaller element of intuition, in the sense of some mental processing to which we do not have conscious access, so cannot consciously verify. In this sense intuition is an unavoidable part of empirical thinking.

    My point is that when doing science and philosophy we should subject our beliefs to as much conscious reflection as possible. That normally involves trying to come up with a decent argument in support of them. (It should be clear from what I've said that I'm not talking about some sort of "complete" argument. The concept of a decent argument is a fuzzy one.) If we cannot do so, we should remain suspicious of those beliefs. Still, it might be reasonable to hold them in a tentative way, if we have sufficient reason to trust our brute (unsupported by argument) intuition on this subject. But I think there are good reasons not to trust our brute intuition (or Searle's) on major philosophical questions.


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