Wednesday, January 20, 2010

A frustration: Evaluating reasoning vs. evaluating premises

Here's a frustration I have in teaching reasoning to students.

I don't teach logic or critical thinking, but do feel compelled to give students a foothold in logical reasoning in introductory level philosophy courses. So in my introduction to ethics courses, I introduce students to the concept of an argument and try to put them in a position to begin evaluating the arguments we confront in the course.

Since this is not a formal logic course, I try to keep things loose or informal, stating that arguments should have (a) good reasoning, and (b) premises that are true (or for which there is compelling evidence). And when they have (a) and (b), I direct them to call such arguments 'sound'. As I said, I'm pretty loose about all of this, particularly (a). I don't distinguish among inductive and deductive arguments, don't go into validity or fallacies, etc. The aim here is simply to get them to appreciate two dimensions of argumentative strength: the reasoning and the veracity of the premises.

So the frustration is this: (a) just seems to pass students by. When we begin to look at actual arguments, students rarely if ever ask questions about, or criticize arguments for, their reasoning. All of their attention is directed at assessing the truth of the premises. And this is so even though I underscore that both (a) and (b) are crucial to arguments; that criticizing an argument for its reasoning is in many respects a more effective form of critique, since often times whether a premise is true is more contentious than whether the reasoning is good; etc. But it seems like in my efforts to teach "reasoning," the students don't latch onto the importance of reasoning!

I'm not sure why (a) doesn't get a grip on the students. (One thought I had is that it requires them to think relationally rather than atomically, which is perhaps more challenging?) In any event, I have three questions for our readers:
  1. Does our experience echo mine — that students tend to evaluate arguments solely in terms of the veracity of their premises rather than the strength of the reasoning?
  2. And if so, what explains this tendency?
  3. How might we, as teachers of reasoning, counteract it?


  1. I've run into this phenomenon over and over again in my critical thinking courses. Students do eventually get over it, but it takes work on their part and ours.

    I don't have any well-supported beliefs about why it happens. Your suggestion about atomic vs. relational reasoning sounds plausible. It may be that beginning students lack vocabulary and good mental models for thinking about the quality of reasoning.

    I don't know of any "magic bullet" to get students to "get it" quickly. I kind of doubt there is one. Here are some things I do very early in my critical thinking courses. Maybe some of them will help.

    (1) Be explicit about the kinds of ways that arguments can fail: (a) one or more premises can be false or (b) the premises can (individually or collectively) fail to give you a good reason to believe the conclusion. This is just another way of making your point about the two features of a good argument—but I think it may help beginners to think about how arguments fail rather than how they succeed, especially if what you want them to do is identify failures in reasoning (i.e., in relevance or sufficiency).

    (2) Give simple examples to illustrate the difference. I imagine you do this, too. Contrast arguments like "Wilbur is a pig. All pigs can fly. Therefore, Babe can fly." with arguments like "You are a student. Some students cheat on their exams. Therefore, you cheat on your exams." I'd recommend that the latter example involve a social situation or a transgression of social norms, since it's often easier for people to see and articulate what's wrong with it.

    (3) Give them visual or mental models to help them understand the support relation. Diagram a simple argument on the board and show how the problem can lie in the "nodes" (i.e., the premises) or the "edges" (i.e., the connections between the nodes). I've sometimes built a little model out of Play-Doh and Pick Up Stix before to show that some premises just aren't strong enough to support a weighty conclusion.

    I think the only real solution, though, is to continue emphasizing the distinction, repeatedly model the kinds of behavior that you want, and explicitly praise students for addressing "good reasoning" rather than (or in addition to) the veracity of premises.

  2. What topic(s) are you having this trouble with?

    At least with ethics topics, what I do does not result in these kinds of logic problems. I emphasize, from day 1, that many people often give moral arguments like this: "This is wrong because __(very short claim here)__" and that usually the connection between that very short claim and the conclusion is not stated or obvious: another premise is needed to make the reasoning complete. I illustrate this with adding 'all men are mortal' to the common Socrates argument example and then say that we're going to be doing the same kind of thing throughout the course.

    Some of the materials I've been using for past few class sessions to introduce these ideas are here:

    Nathan Nobis

  3. A bit more. How do you characterize "good reasoning"? I would bet that many people would think that any argument for a conclusion they think is false is automatically guilty of not being "good reasoning."

    It seems that you could simply introduce a concept of validity (even a loose one that would allow for some non-deductive arguments to be 'valid') and that would help, esp. since you use the term 'sound'.

  4. I have the same experience as you, Michael: students seem to want to focus only on the premises, and not on how or whether they support the conclusion.

    I like David's example argument about student cheating. I might use that one!

    To illustrate validity I present arguments where the students just don't know whether the premises are true or false. I think this is more effective than presenting valid arguments with premises they know to be false, because knowing that the premises are false tends to distract them: they immediately start thinking that the argument is therefore just generally "bad".

    My typical examples of such arguments involve things New Zealand, because that's my background, and 99% of American students have no clue, for instance, what a 'kaka' is and whether or not it can fly... But it's easy enough to come up with such arguments.

  5. I am little confused here (and maybe I am like your students) but isn't reasoning a process of evaluating the premises, anyway?

    It seems the evaluation of each premise is as good of a place to start as any?

    Could you just maybe explain a little further. I have actually taken both a logic course, and an ethics course, already, among many other Philosophy courses. And I am currently enrolled in another batch of Ethic and Logic courses this semester, to achieve my B.A. in Philosophy at the University of Iowa. So I find this very interesting.

    Because to me, what you bothered by is actually the right way to think about these things? But maybe I am missing it? Are you just asking that the provide general arguments against a conclusion, wihtout focusing in on the premises? To me it seems like this would provoke sloopy counter-arguments?

  6. I read this just before teaching a Critical Thinking Class on the distinction between validity and soundness. I printed up copies for all the students and said "Look - professors really are trying to figure out why this is so difficult and help you with it." I don't know whether it helped or not.

    A point I emphasize when introducing the question is that it saves intellectual energy if you have the wisdom to know the difference between that which you can check simply by reading the argument and thinking about it, and that which can only be checked with reference to some external source of information. Also, I point out that seeing something from someone else's point of view often involves imagining what it would be like if things you think are false were true and vice versa, and this is exactly what we're doing when we check to see whether some argument, the truth of whose premises we doubt, is valid.

    For a definition of validity that includes inductive and deductive arguments, see Graham Priest's article in Varzi (ed,) European Review of Philosophy, 4, The Nature of Logic. Priest's suggestion (from memory) is that an argument is valid if and only if there is no situation in which the premises are true and the conclusion false. However, we get decide on the domain of situations over which we are quantifying. Strict deductive validity comes when there is no possible situation, in the broadest sense of possible, in which premises are true and conclusion false. Inductive validity comes when there is no "normal" situation in which premises are true and conclusion false, and of course there can be different standards of normality.

  7. Cont.

    I wanted to add one more thing, a personal example. So I am reading this article on cultural relativism. Now if I said C.R. is wrong because there are object values of evaluation, this would be both an attack on the conclusion of the C.R. argument, but also an attack on a premise behind C.R., namely that there is no object value of evaluation. So where am I going wrong here?

  8. Philosophers Mess:

    Consider the following argument.

    All Model T Fords are black.
    My car is not a Model T Ford.
    Therefore my car is not black.

    You have no way of evaluating the second premise, short of hacking into my facebook account. Nor do you have any independent evidence about the conclusion. But you can see, by evaluating the argument as a whole, that the reasoning is bad.

    Sometimes it makes sense to begin by evaluating the reasoning - as in this case, where evaluating each individual premise is impossible for you. Sometimes it makes sense to begin by evaluating each individual premise.

    The goal we have, as professors, is to teach students how to choose wisely which is the best place to start in any specific case. The problem we have is that they always seem to start by evaluating each premise one at a time, even when we tell them to start by evaluating the reasoning, because they just don't understand our instructions.

    If its now clear, maybe that means I've found the magic bullet!

  9. Thanks for your thoughts, everyone.

    David M - your points are well taken. I do actually guide the students through some arguments, pointing to both sorts of failures. And I really like the visual models idea!

    Ben - you hit the problem on the nose.

    Gazza- I've often thought you're exactly right: Maybe the best way into reasoning is to have students reason about something they know nothing about. I might try the Peloponessian War in all the statements!

    A thought of my own: I wonder if attacking premises strikes students as more ... manly or righteous than addressing the reasoning. Even though by questioning premises you're basically working on the logical terrain set by the proponent of the argument, perhaps students feel it's tricky or underhanded to criticize the reasoning rather than the premises? I like to tell them it's like the difference between judo and aikido. In one, you attack the opponent where she is, and in the other, you let her come at you and have her fall flat on her face!

  10. I'm sorry but I am still kind of missing the point. What would be a response you would get to your syllogism in class, that would be frustrating? I am genuinely curious here, not trying to be hardheaded or anything.

    I logically understand the syllogism and the problem that the conclusion is not supported by the premises, but what's the problem?

    Maybe I just get "it" and that's why I am having trouble understanding your frustration. If this is the case, it probably is as others described, a matter of the amount of effort of the student, or a disconnect in the communication between the parties.

    Do you really have students that are like "well all Model T's aren't black" or "how do I know you don't have a Model T"? Is that the nature of the problem?
    If that is I do think that is a good example to help them think it through.

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  12. Michael -

    I confess that I don't (seem to) have this problem. I use plenty of examples having obviously false premises ("In a world where cats bark, would my cat bark? (Yes) Do cats actually bark? (No!) So if an argument went "All cats bark. Tabby is a cat ....".") and nonsense examples ("Rover is a whisked dog. All whisked dogs are tasty. So, Rover is tasty."; "If you owe, you pee. If you pee, you queue. So, if you owe, you queue.") as Gazza suggested.

    I suppose, then, a recommendation might be to start with arguments whose inferences are valid/cogent (with obviously false/nonsense premises) rather than invalid/incogent (regardless of truth of premises). The psych research shows that toddlers can make the inference about barking cats, but invalidity (such as in the Model T argument) is difficult even for adults. Then move to inferences that are invalid/incogent.

    It's not relevant to this particular question, but I learned a lot about why CR/logic students make the errors in reasoning they do (such as getting the Model T argument wrong) by reading Johnson-Laird's work on mental models. His book (How We Reason) provides a (very long!) overview, but many of his papers are freely available on-line.

    Good luck with the course,

  13. Philosopher's Mess,

    It sounds to me like you're "missing the point" only because you're not tempted to make the mistake that we're talking about. We're taling about student who can't look at Ben's "Model T" syllogism and say, "The problem with it is that the conclusion doesn't follow from the premises. The color of Model T cars is irrelevant to the color of Ben's car, since Ben's car is not a Model T." It sounds like you're not one of those students.

    In my experience, students who don't yet "get it" will do exactly you suggested. They'll say that there might be non-black Model T's—maybe someone repainted one—or they'll ask how we know the color of all Model T's or the color of Ben's car.

    One note, though, about your first comment. Evaluating the acceptability of the premises is a prefectly good place to start. Our concern is with students who never go beyond it. As several of the examples given in the comments show, an argument can have acceptable premises and still be a terrible argument.


    Thanks for the pointer to Johnson-Laird. That sounds helpful. And I really like the use of counterfactuals to get students to accept the antecedent of a conditional.


    I just saw the typo in my first comment: The name of the pig should be the same throughout the first syllogism. Replace 'Babe' with 'Wilbur' in the conclusion. Oops.

  14. I can easily see why this would come up (and be problematic) in a critical reasoning or logic course.

    I do wonder about an ethics course, though: it seems to me that the great majority of the time, "real world" argument specimens, particularly those offered by philosophers, don't suffer from poor reasoning. (Common exceptions, however, might be equivocations, straw men, and false dichotomies). Rather, their logic is usually pretty unobjectionable, and it's the premises that are suspect.

    This is, of course, drawing from my own personal experience, and it may be either that I've been lucky enough not to run into many poorly reasoned arguments, or that I've often been unwitting enough not to recognize poor reasoning when I see it.

    I'm not trying to contradict anything said here, I guess I'm just wondering how often it does come up in an ethics class.

  15. In broad practical terms, it usually makes considerable sense to focus on the truth of premises rather than the structure of the argument. Attacking the truth of the premises is more efficient than attacking the structure of the reasoning for a number of reasons. Of course, Ben gives a natural argument to the contrary above -- but in fact I think that here as elsewhere the majority of students have a more infallible sense of the easy way to do things than those of us who went on to become teachers. In everyday arguments, there is no checking of reference works -- all that one has to do is register disagreement and perhaps, at most, give a reason to back it up. That is, in practice the need to check against an external reference doesn't increase the amount of effort and energy needed to attack the truth of the premises -- because very few people in everyday life go that extra mile of checking at all.

    I haven't noticed this problem myself in Intro Phil, where I deal with these things at some length, nor, indeed, in Ethics, where I don't deal with it at all. In Intro, I focus almost entirely on validity, emphasizing its value, and over and over again noting that the useful thing about knowing that an argument is valid is that you know it can only be refuted in one way, and knowing what premise will make an argument valid is exactly how you tell what the argument is assuming. (While I think it's fairly useful to know that an argument is valid, I think it only becomes useful to know that an argument is invalid if you are doing something fairly technical -- in practical life there are too many enthymemes and nonmonotonic inferences for invalidity to be a pressing matter.) And I rather am inclined to agree with diotimajsh's idea that the bulk of arguments dealt with in Ethics are already fairly good -- at least, even when not clearly so, the lines between 'bad reasoning' and 'reasoning that is flawed but could be modified to be good' and 'good reasoning that nonetheless needs more development than it has received' become very difficult to draw, here, as in any other very practical field.

  16. I have found that Rachels's discussion of the Cultural Differences Argument from *The Elements of Moral Philosophy* is good for bringing home the problem of poor reasoning. I start off by accepting the premise, but then the students can often see that even if it is true, the conclusion does not follow. It is a simple argument with a simple problem.

    Still, students tend to forget this lesson as arguments get more complicated.

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  18. I always illustrate short arguments as "equations" in my intro philosophy classes.

    In my ethics classes we don't spend a LOT of time on informal logic. I spend one week on basic argument construction, the next week on fallacies. I have them browse through some of the tried and true arguments / fallacies resources online, collect some examples, and then come up with examples of their own that mirror these; they are required to put them in equation form in their assignments.

    "Equation form" is basically numbering the premises, drawing a line, then inserting the conclusion underneath. Standard form, except I call these equations. The idea is to get them to think of math when they encounter short arguments.

    This helps illustrate how validity ("adding up correctly") is different from soundness.

    Nathan Nobis' materials have been very helpful to me too.

    On a side note: they are also required to illustrate each argument rule or fallacy with a hand drawn cartoon. This accomplishes little in the way of helping them understand validity. It does help them enjoy learning about different argument rules and fallacies though. They pair up in class, collaborate their assignments, including the cartoon, and throw all of this onto the board in groups. These are fun sessions!

  19. I second (or third) diotimajsh and Brandon.

    1) In published philosophy, the argument structure is almost invariably good. If your course readings are mostly philosophy, then your students are going to gain little traction with argument structure. If you use other forms - editorials, for example - you might have more luck.

    2) Argument structure conversations are short. Basically, the argument is good or it's not.

    3) In real life, the problems with arguments often don't lie in the structure, but in differences over definitions and assumptions which are unwritten. These are much (a) harder and (b) more rewarding to tease out.

    And finally, dubiously: accepting premises that you believe to be false is incredibly hard to do. It's also something that goes against the grain of the way we commmunicate under normal circumstances. You may think you're good at it, but consider your own work. Do philosophers spend lots of time thinking about things they believe to be false? Are there, for example, many atheist theologians? Do you get a lot of utilitarians doing detailed work within the field of virtue ethics? Real philosophers do real philosophy within the zone of what they can believe. Asking your students to do more than that seems, well, let's just say ambitious.


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