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Distinguishing science from non-science

My post about how to distinguish real science from fake science generated some interesting comments, especially over my assertion that we have not as yet been able to come up with an unambiguous way to distinguish science from non-science, and it prompted me to post a follow-up to try and clarify it.

For those interested in this demarcation problem, a good starting point is Larry Laudan’s 1983 paper The Demise of the Demarcation Problem. It is not available online (as far as I know) but it has been reproduced numerous times in various books and is not hard to find. The book But is it science? (edited by Michael Ruse) has papers, including Laudan’s, that argue both sides of this controversy. This post summarizes Laudan’s argument and addresses some of the criticisms of it.

Laudan points out that a satisfactory demarcation criterion must haveboth necessary and sufficient conditions. When people think that it should not be too hard to find ways to distinguish science from non-science, they usually do so on the basis of specifying one or the other, not both.

Why are both necessary? If you specify only a set of necessary conditions, then if something does not satisfy all of them, then you can say definitely that it is not science. But if something satisfies them, all you can say is that it could be science but not that it definitely is. For example, take the necessary condition that a scientific theory must be falsifiable. The theory that the moon is made of green cheese is falsifiable so it meets the necessary condition. But is it science?

Conversely, if one specifies a set of sufficient conditions, then if something satisfies all of them, then one can say definitely that it is science. But if it fails to satisfy some of them, then you cannot definitely say that it is not science. It may still be science. Again, suppose we create a set of sufficiency conditions of which one is the requirement that a theory must be falsifiable. Currently string is not currently falsifiable since it does not make specific predictions that can be tested. So that means that we cannot definitely say that it is science though it may well be.

The requirement that one must have both necessary and sufficient conditions for suitable demarcation criteria is generally true. But there is also an auxiliary condition at play. When we are creating demarcation criteria for something, we are chiefly interested in a class of objects (or theories) for which we already have some idea of what belongs and what does not. If we create demarcation criteria that fail to include members that should obviously belong (based on our intuitive sense) or includes those that obviously should be excluded, those criteria would not be suitable either. Demarcation criteria that ended up classifying general relativity as not science and astrology as science would be looked at askance.

As a trivial example to illustrate these points, suppose that I want to be able to distinguish between chairs and non-chairs. I could specify a necessary condition that a chair must have four legs. If something has three legs, then it is definitely not a chair, according to my criterion. But if it has four legs, all I can say is that it may be a chair or it may not. It may be a dog.

Similarly, suppose that I specify a whole set of detailed conditions for a chair (it must have four legs, have a horizontal seat and an upright back, and be at a height suitable for sitting on) and say that any item that meets all those conditions is sufficient to certify it to be a chair. Undoubtedly many traditional chairs would meet those criteria. But what about a chair made by incompetent carpenter in which the seat is not horizontal or the back is not upright? It does not meet the sufficiency criteria and so we cannot certify it to be a chair. But it may well be a chair. Many modern chairs with their unusual geometries may also be excluded. In fact, the more rigorous one makes the sufficiency criteria, the more likely one is to have things that one thinks should belong not make the cut and be left in limbo.

And what about a sofa or a bed? They would meet all the sufficiency criteria to get the certification of being a chair though neither is what we normally consider to be a chair. So this fails the auxiliary test too.

That is why the necessary and sufficient and auxiliary conditions are required for satisfactory demarcation criteria. With chairs it may be possible to construct such conditions but Laudan thinks that this problem is insoluble for the science/non-science split. Others have challenged his view but not (in my view) conclusively. But his essay is definitely an excellent starting point for understanding the issue.


  1. jamessweet says

    As with the problem of induction, I feel that the demarcation problem is ultimately intractable, but that it doesn’t matter on a practical level. A thing can be true without there being any way to prove it. Ultimately, I feel inductive reasoning cannot be justified without appealing to circular logic; and while I haven’t given it as much thought as the former, I suspect that the demarcation problem cannot be solved in a way that works for every possible example — but nevertheless, someone who rejects inductive reasoning or refuses to acknowledge that science is distinctly more reliable than other “ways of knowing” will rapidly find herself in an epistemcally untenable position. It becomes impossible to argue anything without first granting a few assumptions. And luckily, they happen to be assumptions that virtually everyone shares in practice, even if they may argue in philosophy class that they don’t.

    Not that I am dismissing such things as not worthwhile; at the very least, I find such discussions fascinating. But I’m not losing sleep worried that perhaps there is no such thing as science, or that inductive reasoning is invalid. Such discussions are at the very least interesting, and quite possibly enlightening. But if such endeavors should fail, it’s not really a problem.

  2. eric says

    Like James, I fail to see this as a significant issue for society in general (it may be one for philosophers). Most practical issues that involve determining the “scientificness” of something involve resource allocation. For example: which proprosal(s) should we fund, and which material(s) should we teach in a science class.

    Now for both of those, you mostly don’t need any formal demarcation of science and non-science. You only need comparative measures. Which research proposal is better than the others. Which historical theories or current theories are most important to teach. (I say mostly because both funders and science educators may have minimal”necessary” criteria that something must meet to get funded or taught. Those will rarely come in to play, however, because the reality of the situation is that we have more good material to teach and fund than we have time and money to cover. Necessary criteria may be needed to push back against creationism being taught in HS biology – which is important – but will not find much use outside of that issue).

    And just FYI, AFAIK Laudan has also argued that creation science counts as science for his demarcation criteria and that McLean was wrongly decided. So while he may have a point that some sort of criteria are needed, I would be sceptical about his preferred criteria, saince they probably conut as ‘science’ things that most scientist would consider complete bunkum.

  3. Paul Neubauer says

    My wife, who teaches Linguistics, has a demonstration she does in one of her courses. (I used to be a linguist, but left the field for computing.) The students are given the problem of defining the difference between a “cup” and a “mug.” The task is, of course, iterative and the students are trying to improve their criteria throughout the class period. As each “improvement” is suggested, she will produce one or more sample objects from her (ever-growing :-) ) collection of related objects and challenge the students to apply or modify their criteria to take the new object into account.

    Some of the objects end up being dubbed a “glass,” or a “flask,” or a “pitcher,” or a “stein,” or any of a number of other terms, but the upshot of the demonstration is that specifying a clean definition, in the form of a set of necessary and sufficient conditions is, in general, not really workable. Definitions, as we are familiar with them are just not generally possible. It is more generally the case that we humans have some kind of prototype in mind for a word and tend to judge the applicability of the word to a specific object or instance based on our mental prototype. We normally learn words in our native languages by example. We see (possibly in a metaphorical sense of “see”) exemplars of a “cup” or “mug” and eventually, we develop some form of concept where some objects fit the concept better than others.

    If we cannot “define” the difference between a “cup” and a “mug” in a way that can satisfy ordinary, competent, native speakers of English, I think it’s pretty unlikely that we can “define” a concept like “science,” which is not only slippery, but actually somewhat controversial, in a completely satisfactory way.

    FWIW, I agree with eric @2 that “creation science” should not be defined into the category “science.” Unfortunately, I don’t know how to exclude “fake science” if we were to admit that “definitions” are not really definitive. I suspect that we may be able to recognize (at least some) necessary conditions even if we cannot specify a complete set of necessary and sufficient conditions. This may be problematical for legal purposes since the notion of “definition” is deeply ensconced in much of our legal system. It may also be problematical for many philosophers due to the widespread committment to binary rather than fuzzy logic. Still, I would like to suggest that fuzzy logic may be closer to what people do when we use natural language.


  4. Mano Singham says

    I think you are quite right. I think it was the philosopher Ludwig Wittgenstein who suggested that the best we can do is to intuitively recognize what he termed ‘family resemblances’ that enables us in most situations to judge into which category things fall, rather than using verbal formulations and criteria.

  5. mnb0 says

    Laudan is right, which is essentially the reason why I think it better to concentrate on identifying fake science. Sure some fake stuff will slip through the filter, but that’s still better than let everything pass, don’t you think? We can use the chair analogy here as well – I rather have 90% correctly identified as a chair than 50%.

  6. Jared A says

    I think it is worth pointing out that the philosophers being polled here seem more characteristic of analytical philosophy (most american philosophers are), and I believe that there is a rather strong departure in how analytical and continental philosophy deal with ideas. Continental philosophers are much more comfortable dealing with language and culture and how these things relate with our understanding and ideas.

    The other day I had a very nice discussion with my brother–who teaches philosophy–about understanding and ideas. His premises were more compatible with what Paul was saying in #3 than they were with the analytic philosophies represented in the article– which may be unsurprising given that he studies language and culture and himself primarily identifies with the continental tradition.

    I gather that his major point would be that understanding is by nature iterative for the same reason language is–like in that nice mug example in #3. Categories, after all, are only as useful as they are. :)

  7. says

    I must say that this seems rather muddled to me, when I think the solution is actually quite straightforward, and, in hindsight perhaps, rather obvious.

    It is true that it’s difficult if not impossible to provide a completely rigorous, necessary and sufficient, definition of science. Yeah, so? To me this goes to show the failure of the criteria of being ‘necessary and sufficient’ in the first place.

    Ah, but if we don’t have ‘necessary and sufficient’ conditions for X or not X, then we can’t do this that or the other…. (E.g. can’t provide a logical proof of some activity being ‘scientific’ vs. ‘non-scientific’.)

    Again, so?

    What are the practical consequences? That is the only question which seems relevant to me. In fact, it is exactly that question by which I judge just about everything. Boiled down: Does it work?

    And this leads directly to what distinguishes ‘real’ science vs. non- or pseudo-science. Science works. Non-science doesn’t. To be more specific, science is that activity which humans have developed which emphasizes the search for hypotheses and theories that work (actually, really work) to explain and predict the reality we find ourselves in. You really don’t have to get much more precise than that.

    I think it’s a mistake to get bogged down in such word-play about the so-called ‘demarcation problem’. It’s very much akin to questions of ‘souls’, or ‘qualia’, or a crisp definition of ‘life’ or what it is to be ‘human’.

    In some cases, such as anti-scientific post-modernist (or other, e.g. religious) attacks on science, it’s more akin to ‘souls’, ‘spirits’, ‘true consciousness’, whatever. Useless concepts, to put it mildly.

    In other cases, it’s more of a misguided attempt at humility, as in the cases where I often hear people proclaim, “Ah, but we can’t really know anything perfectly!” And I reply, “Ah, but we *can* know *some* things, even if not perfectly.” Who said we have to have perfection in order to have usefulness?

    Is a thing with four legs a chair? It is if I can use it to sit on it, and if I care to call it by the sound or written word, “chair”. If I happen to speak French, it would be a “chaise”, but still fulfill the role of the conceived-thing of what the English word “chair” refers to.

    What about three legs? Yep, a ‘chair’ if I can sit on it and choose to call it a chair. How about two legs? Sure, why not? One? Yes, they exist; yes, chairs.

    You could even have a chair with no legs at all, connected to a wall, for instance, or suspended from a ceiling.

    I might find a rock and sit on it, and call it a chair. Why not? Who’s stopping me? Language is not so rigid.

    You can even make chairs entirely out of people, as one party game I participated in once proved to me.

    Why should it matter if I call it a ‘chair’ or ‘hair’, or ‘air’, or a ‘boomfrazzlegazzle’? If I can sit on it, it ‘works’ as a chair, and that’s all that really matters in the end.

    Likewise, if ‘science’, whatever that is, can help us find true theories and hypotheses, who cares if it happens to involve ‘falsification’, or ‘peer review’, or ‘significance tests’, or whatever? If it works to help find true theories and hypotheses, it ‘works’ as science. If it doesn’t, it ‘fails to work’ (or, in some cases, ‘works less well’, as the case may be). *That* is how *everyone* distinguishes science from non-science *anyway*, so why not use *that* as our ‘definition’, i.e. Does it work?

    Not specifically to define science, but I’ve written previously about this idea of pragmatism and prediction, which I would urge more people to start thinking this way. It really cuts through a lot of pointless (when you really get down to it) quibbling over ‘differences that make no difference’. See

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