Plausibility and Same-Sex Marriage

In philosophical discussions, we bring up the notion of plausibility a lot.  “That’s implausible” is a common form of objection, while the converse “That’s plausible” is a common way of offering a sort of cautious sympathy with an argument or claim.  But what exactly do we mean when we claim something is plausible or implausible, and what implications do such claims have?  This question was, for me, most recently prompted by a recent pair of blog posts by Justin Weinberg over at Daily Nous on same-sex marriage.  In the posts and discussion, Weinberg appears sympathetic to an interesting pedagogical principle: instructors may legitimately exclude, discount or dismiss from discussion positions they take to be implausible.*  Further, opposition same-sex marriage is taken to be such an implausible position and thus excludable/discountable/dismissable from classroom debate.  Is this a legitimate line of thought?  I’m inclined against it, and will try to explain why in this post.**   


What is plausibility?

            Right off the bat, we should try to get clearer on the concept of plausibility.  Unfortunately, there doesn’t seem to be a rich literature on this (Though I encourage commenters to enlighten me here!).  Plausibility is admittedly a well-explored issue in epistemology, especially since a 1981 article by Dennis Packard, but the literature there seems to presuppose without discussion a background understanding of what plausibility is, and concerns itself with formal ranking models.  More usefully, Nicholas Rescher (2005) has offered 3 different (plausible?) conditions for a claim’s being plausible: (1) When a preponderance of evidence favors it; (2) when it holds in more possible worlds than its negation; and (3) when credence in it passes some probability threshold, like 1/10.  I don’t like definitions (1) and (2) as the notion of plausibility collapses into roughly what one is justified in believing, which is too narrow.  (3) is more appealing, as it straightforwardly allows one to say one (weakly) believes X is correct but that ~X is plausible – which I take it is sometimes how the notion is deployed.

            The probabilistic notion has its own issues.  How, for instance, are we supposed to convert our moral beliefs into proper credences?  I myself am baffled when asked to assign such numbers, at least to non-empirical questions of morality.  Maybe we can fudge it – there’s some level of confidence, intuitive to most of us, above which we would rate some claim as ‘plausible’.  But then we have to ask, how could such a fudgy notion have the sort of pedagogical and dialectical role it is meant to have?  In particular, why should falling below that threshold rule some topic out from discussion and debate?


The role of implausibility

            One route is argument by analogy.  Weinberg brings up slavery in this context – we’re so confident slavery is wrong, there’s no need to take pro-slavery arguments seriously in the classroom or during debates.  Weinberg and others are similarly so confident that same-sex marriage is OK that it should be similarly excludable.  I worry this is too exclusionary, though.  As philosophers, we often take strong positions on issues; for instance, many deontologists are absolutely convinced that utilitarianism is incorrect due to its narrow value focus, ignorance of central moral issues and absurd implications.  But it would be inappropriate for them to exclude utilitarianism from classroom discussion on these grounds, and decline to engage in debate with utilitarians on the grounds that they’re just silly. 

            Perhaps we could differentiate things like utilitarianism’s alleged implausibility from slavery’s (and same-sex marriage’s) by adverting to the latter’s association with bigotry and disrespect (though Weinberg specifically rejects this strategy in comments).  Slavery was historically often justified on racist grounds, and some argue same-sex marriage is opposed on homophobic grounds.  So the principle would be something like: X is excludable if it is (a) implausible and (b) expresses a bigoted/disrespectful position.  Or maybe (b) could be fleshed out in terms of human rights?  The idea would be that some ideas are both so unlikely to be true AND harmful that discourse over them is inappropriate. 

            I would say such an exclusionary principle is plausible (see what I did there?) but still misguided.  In fact, instructors should be engaging with arguments for even ‘beyond the pale’ institutions like slavery, as well as ‘obviously’ immoral activities like lying and murdering.  Understanding why some position is (deeply) misguided can be illuminating, causing – as Mill notes – one’s own considered views to become stronger and more clear in contrast.  For example, Hare’s famous Juba and Camaica thought experiments show that utilitarians have to address whether slavery is intrinsically wrong, if so why, and if not how to reconcile that implication with strong contrary intuitions.  Even if they ultimately agree we shouldn’t enslave people, their moral theory becomes more clear and well-worked out when pressed to explain why.

            An alternative analogy wouldn’t be to slavery, but empirically certain yet politically controversial matters like climate change, or uncontroversial issues like the falsity of phlogiston theory.  A class on climate change may legitimately dismiss climate denialism based on the massive amount of evidence, and a class on chemistry may legitimately dismiss phlogiston theory – because of the implausibility of climate denialism and phlogiston theory.

            In the case of climate change, I’m not so certain we should dismiss denialism.  Again, given that evidence is supposed to be so decisive against denialism anyway, exploring that evidence would only provide students with a proper understanding of the issues.  That understanding is important for engagement in further debates, and better than mere reliance on expert opinions.  Indeed, by having students engage with denialists, one can help them become the sorts of experts that can refute denialism.

            On phlogiston theory, by contrast, I’d agree it’s not worth discussing outside a history/sociology of science course.  But this because there’s no current controversy over phlogiston theory, almost no one takes it seriously, and it is mostly irrelevant. 


Application to Same-Sex Marriage Debates

Just as we should be inclusive about discussion of ‘settled’ issues like slavery and climate change, we should be inclusive when discussing and teaching about same-sex marriage.  By engaging with opponents, those who support marriage equality can flesh out what they take marriage to be (an issue recently emphasized by Spencer Case, in response to Weinberg), what is at stake in the political debate and where, exactly, they disagree with interlocutors.  Dialectically, this allows for more rigorous and convincing argumentation.  Pedagogically, this allows people to properly grasp what is going on in the broad debate, learn about the commitments that go along with various positions and come to their own opinions based on reasoned consideration rather than group-think or rhetoric.  If proponents of same-sex marriage are right and opposition is indeed implausible, they should be confident that many benighted opponents will come around when faced with rigorous discussion (as, I believe, has been the case).

            To be sure, there may be *other* grounds to exclude a topic like same-sex marriage from discussion.  It’s not relevant to every class and discussion.  And perhaps, if it is a non-issue in society, one could exclude it due to more general irrelevance or obscurity (Weinberg sometimes adverts to this sort of reasoning as well).  Student interest, general relevance and practical import are, to my mind, perfectly good grounds for designing a syllabus. And even steering debates away from obscure issues that others in a classroom just don’t care about may be fine.  But given that same-sex marriage is such a relevant topic politically at the moment – with the US Supreme Court set to make a landmark decision on the issue in the next year and many nations’ policies in flux – we are not likely at the stage where exclusion of the topic is legitimate on irrelevance or obscurity grounds.

            But of course, all this applies to the meta-issue of whether and how same-sex marriage should be discussed – that is, we should have a healthy debate over whether or not Weinberg is right.  And even by Weinberg’s lights, this is the case – he doesn’t seem to think that support for a decision to engage with same-sex marriage opponents is implausible.  Which, in turn, means Weinberg should at least be on board with a classroom discussion and debate (when relevant) over this very issue: should proponents of same-sex marriage seriously engage, in the classroom and beyond, with opponents whose views they find implausible?  Though I would answer ‘yes’, I also think this is itself an interesting and worthy topic for discussion and debate.



*At least, I take this to be Weinberg’s position – it’s not explicitly stated, and this is what I infer from his comments.  Also, notably Weinberg is fine with talking about same-sex marriage opponents’ positions more broadly – but more to explore why they’re so deeply mistaken, rather than inquire as to whether or not they’re correct. It’s the latter sort of open-minded inquiry into veracity that I am interested in here.

** I argue that Weinberg is mistaken to exclude debate over same-sex marriage even if same-sex marriage opposition turns out to be implausible; strictly speaking, I’ll here be neutral on whether such opposition is in fact implausible.

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8 Responses to Plausibility and Same-Sex Marriage

  • Peter English says:

    My apologies for focusing only on the plausibility concept and ignoring the same sex marriage topic here…

    For me, plausibility and implausibility carry very different weights.

    I am a doctor; and I have to consider evidence as to whether or not a treatment works.

    Snake 0il salesmen, throughout history, have grown rich from promoting seemingly plausible but useless treatments to a gullible public; and many new drugs or other treatments for which we have great hopes based on their plausibility have turned out to be ineffective. So, when assessing whether a treatment is likely to work, plausibility is a poor guide.

    Implausibility, on the other hand, is a far stronger indicator. It’s true that some treatments have worked despite us not – at the time – having an explanation for why they would work. Such efficacy may well have seemed implausible until the science was better understood. But in general, implausibility is stronger evidence that a treament is likely to work than plausibility is for a treatment’s efficacy.

    Certainly, treatments where the mechanism of action seems implausible – such as the idea underlying homeopathy; that almost infinitely diluted substances will cure diseases which happen to produce the symptoms that high doses of the substance might produce – require much greater standards of proof before it can be considered likely that they are effective, than treatments with a plausible mechanism of action.

    • Anders Sandberg says:

      I find this comment interesting, since I am currently working on a paper dealing with cryonics. Whether cryonics will eventually work is unknown (we can certainly freeze dying people, but whether they will be ever resuscitated is unknown). However, much of the debate (and some legal cases) deals with whether this is plausible or implausible. Some people think cryonicists are snake oil salesmen peddling an implausible treatment (making them rather bad salesmen), while cryonicists of course think they have a plausible chance of being right (even if the probability of success does not have to be *high*; it just needs to be high enough to make it rational to cryosuspend patients).

      Should one regard the possibility of cryonic resuscitation as implausible since we do not yet have a blueprint for how it could be achieved? One can marshal historical analogies for how the concept of death and the practical limits of who can be resuscitated have shifted, but this seems to be a meta-plausibility argument that one should not judge the first argument too strongly – we should keep an open mind, especially since the future can be long and strange.

      Conversely, empirical results that current protocols preserve various important properties (such as neural connectivity, LTP and some organ function) certainly boost the plausibility of cryosuspension not doing too much damage, but since we do not know what threshold of preservation will be needed in the future this might be far less compelling than in other cases where we aim at an ultimate well-defined hard target and can tell how much we have advanced towards it.

      Together, we get not just a messy debate about whether cryonics is plausible or implausible, but how to judge the evidence promoted to support these claims. It seems there are assumptions about possible pathways to the goal (or the eventual lack of such pathways) that strongly affect how much evidence changes the plausibility/implausibility.

  • Anthony Drinkwater says:

    I’m rather saddened by the claim that implausibility might be considered an objection in philosophical discussion. To say of something that it is implausible is surely simply to say that it is, on the face of it, hard to believe : but this has nothing to do with its truth.
    It seemed implausible that Bradford City should beat Chelsea this afternoon after being 2:0 down – but it happened.
    It seems implausible to some that a lottery draw of 6 numbers from 100 should produce the numbers 1 to 6 : but those numbers are just as likely to come up as any other 6 numbers.

    But thank you for your post, Owen : in following up your links I discovered the Harassment Policy of Marquette University :

    “Harassment is defined as verbal, written or physical conduct directed at a person or a group based on color, race, national origin, ethnicity, religion, disability, veteran status, age, gender or sexual orientation where the offensive behavior is intimidating, hostile or demeaning or could or does result in mental, emotional or physical discomfort, embarrassment, ridicule or harm.”

    Read it slowly and remove a few words and you’ll see that it forbids, inter alia, “conduct that could result in emotional discomfort or embarrassment”.

    This policy is clearly plausible (it exists). Roll over JS Mill and Voltaire ! (And don’t try to sell Charlie Hebdo on campus..)

  • Davide says:

    Perhaps not what the discussion is about, but I hope that the vigorous debate now means that, in X years time (20? 50?100?), the people who are arguing against same-sex marriage will not be described by historical relativism as ‘products of their times’ like it is often done with those who supported and enforced slavery, sexism, or other institutions we now accept as unethical.

    Basically: their defenders should not get to claim that same-sex marriage was a minority view point or not something that could actually be done when there is such support (and good arguments) for it.

  • Justin Weinberg says:

    Let me clarify my view. In considering whether to teach about the moral and legal issues regarding same-sex marriage in a class like “contemporary moral problems,” I have explicitly mentioned two conditions, and implicitly there’s a third. I think that these three conditions, taken together, can justify a decision not to teach a topic. Here they are, in general form:

    (a) There are no plausible arguments in favor of what would be one of the main positions in a dispute on the topic.
    (b) The topic is not a live or controversial issue for the people I’d be teaching it to.
    (c) The topic is not essential to the course, and there are plenty of other topics that could be substituted in for it (of which (a) and (b) are not true) without any detriment to the goals of the course.

    When these three conditions are met, it’s permissible for an instructor to not teach the topic.

    I think these conditions are met in regards to the claim that straight and gay couples should have different marriage rights, and also in regards to the claim that the moral permissibility of sexual activity depends on whether the activity is heterosexual or homosexual.

    This argument does not imply that it is necessarily a bad idea to teach the topic—there could be countervailing reasons to do so. And there could be good reasons to teach something quite close to the topic. So, even though I think these conditions are met in regards to the two claims mentioned in the previous paragraph, I have taught them recently. I’ve taught the former because there are interesting questions of political liberty and compromise that the topic can be illustrative of, and I’ve taught the latter because it gives me a chance to talk to students about the ways in which “natural” and “unnatural” are carelessly bandied about in popular moral discourse.

    My position raises a couple of questions, of course, most obviously: what is “plausibility”? I don’t know the literature on this so feel free to help me out here, but as I said in another comment (, I am using “plausible” as an intermediate position that lies somewhere between “clearly mistaken” and “convincing.” So some arguments are plausible but ultimately unconvincing.

    What makes an argument plausible? Restating what I said in an earlier comment, I think an argument qualifies as plausible if it isn’t fairly easy to show that its premises are false. The premises may in fact be false, and it may be possible to show this, but, so long as it takes more than a quick counterexample or small straightforward moves to do so, we can count the argument as plausible. Granted, there are some vague terms in this account of plausibility, but I don’t think I know how to be more specific about it just yet.

    • Bernard Randall says:

      I would suggest that there are problems with asserting both (a) and (b) for this topic.

      To take (b) first, it is surely a matter of clear public debate and controversy, and students ought to be able to assess and engage in that debate. If by “not controversial for the people I’d be teaching” you mean they’ve already decided without any thought debate, then there is perhaps a duty on the educator to unsettle prejudice – even if only long enough to show that it is not merely prejudice. Moreover it is likely to be a live issue for some people with whom the students come into real life contact – some religious believers, members of an older generation such a s their own grandparents perhaps.

      On (a), you would presumably be dismissing out of hand all arguments based on religious thought. But whilst religious texts cannot simply trump ethical thought they have a place in the discussion. So, for example, it seems to me thoroughly implausible (on empirical grounds) that “all men (sic) are created equal” unless one comes from a Judaeo-Christian starting point. That aside, gay and straight marriage in the UK are not exactly equal (as regards adultery), and so there must have been some plausible reason in the mind of Parliament for making them different (but we might well argue they got this wrong). Or is it obviously implausible that, since marriage as a legal institution is in significant part about inheritance rights, and children are a major part of inheritance, there might be grounds for framing marriage laws in a way which distinguishes gay (or old?) from straight (young?) couples? That might run very foul of ideas of fairness, minimal state interference or any number of other things, but I’m not sure that it’s trivial or uninformative for the students to practice constructing the arguments.

      But (c) is surely always true – any course has limited time and cannot cover absolutely everything, so the educator makes some choices.

  • Dave Frame says:

    The thing I don’t like about excluding things on the basis of plausibility is that it might throw out lots of babies alongside lots of bathwater. “Climate change” is not one thing. A dispute about basic radiation physics would be just as dumb as a dispute about phlogiston – no one seriously pretends that CO2 and H2O molecules don’t absorb radiation at the relevant wavelengths. But reasonable people can and do argue over the strength of the cloud feedback. (And reasonable people argue (a lot) over energy policy and other responses to climate change.) The idea that an ethicist or social scientist might ban heterodox opinions on climate change would trouble me, since while heterodox views on some bits of the problem might be dumb enough to warrant a ban, many other heretical views might actually be perfectly reasonable. I have similar issues with marriage debates. To me, marriage as a social institution is a response to a particular suite of problems – creating conditions that encourage time-consistent behaviour in a situation where important externalities arise against a back-drop of a large number of principal-agent issues. Personally I’d like to be able to chat to people about that, including relevant ethical dimensions, without having any/all the questions I have ruled out – a priori – as implausible on the basis that other people who have other questions have suggested something that is implausible. That would be like me dismissing questions you might have about cloud feedbacks on the basis that someone else said something daft about radiation physics.

    In other words, real issues might be too variegated for exclusion to work without suppressing legitimate debate. I guess it’s a type 1/type 2 error thing – you can avoid lots of “implausible” debates through exclusion, but the price will be intolerance of some legitimate debates; alternatively you’ll have to put up with lots of implausible stuff to make sure you sample some reasonable heterodox views. (But unless ethicists become experts on everything, I don’t see any option other than making such a choice.)

  • Joe says:

    “In fact, instructors should be engaging with arguments for even ‘beyond the pale’ institutions like slavery, as well as ‘obviously’ immoral activities like lying and murdering. Understanding why some position is (deeply) misguided can be illuminating, causing – as Mill notes – one’s own considered views to become stronger and more clear in contrast. ”

    Thanks for the interesting post and discussion. That said, I just wanted to note that this is basically the point at which you engage with the best version of the position you’re attacking, and that your response to it–this sentence–is just a speculative empirical claim.

    Moreover, the association with bigotry reveals something that goes unaddressed in this post, i.e. the ways in which “discussions” of these issues can and do devolve into subtle attacks on the very groups who are the traditional targets of bigotry. So even *if* your empirical claim is true, and engaging with such positions can “strengthen” our own positions, there is still the open question of whether a professor ought to risk a situation in which one of their students launches thinly veiled hate speech at other members of the class. In other words, a professor’s sole aim is most certainly not merely to strengthen his or her students’ positions, it is also to run an ethically acceptable classroom that allows each member to participate without fear of attacks or denigration. It’s more than a little curious that this element is missing from your post.


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