Posted by: Justin | July 19, 2010

Full rationality

I’ve just finished reading Michael Smith’s The Moral Problem, and I have an issue with his account of the fully rational agent (pp. 155-161). He borrows, and then amends, Bernard Williams’s account. On this account, the fully rational agent must meet the following three conditions:

(i) No false beliefs

(ii) All relevant true beliefs

(iii) Deliberate correctly

Smith takes some time to spell out what he has in mind by (iii). But I want to take issue with (i) and (ii). My question is simple: why think that rationality – even full rationality – requires omniscience, or even omniscience about the relevant matters? Some prima facie evidence against this account would be a case like the following:

Misleading evidence. Phife Dawg is supposed to meet Q-Tip at the studio at 10:00 to record a new album. Q-Tip never misses a recording session, and is always on time. As Phife steps into the elevator up to the studio at 10:05, Jarobi, who never lies, steps out and tells him that Q-Tip is upstairs waiting for him. When Phife gets to the door of the studio, he hears the distinctive beep of Q-Tip’s Skypager, which Q-Tip never lets out of his sight. This is all of the relevant evidence that Phife has, or could be expected to have. Phife then finally forms the belief that Q-Tip is in the studio. But as it turns out, all of this evidence is misleading. Q-Tip is not in the studio; he’s at home asleep.

So Phife has a false belief. Thus, by the account of full rationality – in particular, condition (i) – Phife is not fully rational, because he has a false belief. Though we might agree that Phife is not fully rational for some reason, I think it is implausible to think that he is less than fully rational in virtue of his false belief. In fact, forming this false belief seems to be the most rational belief Phife could form, given his evidence. So (i) is implausible. Rationality does not require one to have only true beliefs.

If Q-Tip is in the studio, then Phife should go in to record.  If Q-Tip is not in the studio, then Phife should go look for him. So the belief Phife forms about Q-Tip’s location is practically relevant. So Phife lacks a relevant true belief – the belief that Q-Tip is not in the studio. Thus, by (ii), Phife is not fully rational. Though we might agree that Phife is not fully rational for some reason, I think it is implausible to think that he is less than fully rational in virtue of his lack of a relevant true belief. In fact, forming the belief that Q-Tip is not in the studio would seem to be irrational, given Phife’s evidence. So (ii) is implausible. Rationality does not require omniscience, even about relevant matters.

These problems might not seem terribly important, but I think that they actually cause a bigger problem for Smith’s analysis of normative reasons. That analysis is the following:

Reason: S has a normative reason to A in circumstances C iff S’s fully rational self would desire that S A in C.

Smith wants to use (i) and (ii) to block reason-ascriptions in cases like Williams’s gin/gasoline case. In this case, S has a glass in front of him which he believes (for good reason) to contain gin. But in fact, it contains gasoline. So, Smith wants to say (I think), S has no normative reason to drink the stuff in the glass. This is supposed to be the result delivered by the analysis, since S’s fully rational self would not desire that S drink the stuff in the glass, since he would know that it contained gasoline instead of gin (by (i) and (ii)). But if I’m right that (i) and (ii) are implausible, then Reason will not obviously deliver the verdict that Smith wants in this case. (Note: I disagree with Smith that S has no normative reason to drink what’s in the glass, but that’s another issue.)

Disclaimer: I haven’t done a literature search, so I don’t know if I’m the first person to bring any of this up (I doubt it).



  1. i think Smith might be thinking about things like this.

    There is a sense of rationality which is very objective. This is the sense which we invoke when we say things like one should believe only what’s true. In this sense, (i) and (ii) are required because there is a type of rational criticism one can give of people who fail to have (i) and (ii). Namely, one can criticize them as ignorant. Phife may be criticized on these grounds.

    I think he would also admit there is a sense of rationality which is about what you should believe given the available evidence, but deny that this is the sense he has in mind.

    That’s my thought at least….

  2. It seems like your objection to Smith is that you think his three conditions go beyond what we should require for being “fully rational”. It is worth noting that sometimes people who propose analyses like “Reason” include a separate “fully informed” condition (in addition to their “fully rational” condition).

    But, set aside that choice of terminology. It seems like there is an interesting view that says, you have a normative reason to A in C just in case, were you such that you met conditions (i)-(iii), you’d want yourself to A in C.

    I haven’t read the book, is Smith interested in offering (i)-(iii) as a substantive analysis of “being fully rational”, or is it fair to treat “fully rational” as a bit of technical terminology on his part?

  3. Just a quick reply (hopefully I’ll have more to say later). It’s a good point that Smith could just say that he’s dealing with a more strict notion of rationality, or introducing a quasi-technical term. But one worry I have about this strategy is that Smith bases his analysis on what he takes to be a platitude about rationality, which is supposed to be something you have to believe in order to count as being competent with the concept. This platitude is that we have reason to do what our fully rational selves would desire that we do (as Smith notes, the platitude is very close to the analysis already). But I think that the ordinary notion of rationality doesn’t require omniscience. So the notion Smith adopts can’t be the notion in the platitude. This doesn’t show that his analysis is wrong, of course, but the point remains that he wanted to base his analysis on this platitude.

  4. I think Shyam and Lewis are right that Smith has something of a technical term in mind.

    However, more in line with Justin, I’m not sure Shyam is right that there is some ordinary sense of “irrational” that applies to mere ignorance. I doubt there’s much ought-talk that applies to purely having a false belief without negligence. We then start to shift to mere evaluative- and perhaps reasons-talk. We say it would be good to believe what’s true, but it starts to sound like more of a stretch to me to say that one ought to do that. It might be the aim of belief or whatever, so maybe you can criticize the mental state for being dysfunctional, but criticisms of the agent—when there is no negligence, of course—lose any grip on my ears.

    Here I’m with Parfit, I think, that rationality is more internal and reasons are decidedly external: “While reasons are provided by the facts,…rationality…depends instead on our beliefs.” Here’s a case and statement of his that Justin would probably like:

    if I believe falsely that my hotel is on fire, it may be rational for me to jump into the canal. But I have no reason to jump. I merely think I do. And, if some dangerous treatment would save your life, but you don’t know that fact, it would be irrational for you to take this treatment, but that is what you have most reason to do.
    (“Rationality and Reasons” 2001, p. 17.)

    Smith could certainly say it’s a technical term he’s using. (Although, if he meant this, he should have been clearer—negligence!) But then Justin is also right, I think, that this move causes more problems for him than he’d like to admit. Smith’s whole methodology here is conceptual analysis. So pretty much every damn claim he makes is meant to be a priori and grounded in intuition. The success of that strategy as applied in Smith’s book becomes much more questionable when he’s covertly employing technical terms left and right. After all, it’s difficult to judge the truth of a platitude a priori when it has technical terms, especially when they seem to differ throughout the book!

  5. @Justin,

    The view in question seems more plausible than one that strictly adheres to your reading of the platitude to me. However, I think you are being unfair, in that, it isn’t as though the view has nothing to do with rationality (as you think about it). My point was that the view amounts to requiring something like what you would term “rational and relevantly informed”. The platitude sounds about as good (actually: better) if you say “you have reason to do what your rational and relevantly informed self would want you to do”.

  6. So, the ordinary notion Smith is after is immunity to rational criticism. I gave a bit of rational criticism that spoke to (i) and (ii). It is true that we also want to explain the sorts of things you mention when talking about Pfife (so, for example, we want to explain why we would criticize if Pfife truly believed that Q-Tip was not around). But, they don’t have to be explained through (i) and (ii). They can be some other explanation due to (iii).

    This is, in fact, how I see Smith’s picture working. I think, for him, cases like yours are explained by certain patterns of attitudes the fully rational agent would have. In particular, if the fully rational agent believed p1….pn and if p1…pn are sufficient or conclusive evidence for q, the fully rational agent believes q as well. The intuition about Phife’s rationality can be explained by the idea that if he were to believe that Q-Tip were around then he would have a pattern of attitudes which are not like this. He would believe p1…pn which are conclusive evidence Pfife is around, but fail to believe Pfife is around.

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