Monday, May 31, 2010

Hume's Inaccurate Predictions

In the introductory section of his Enquiry Concerning Human Understanding, Hume contrasts two ways of doing philosophy. While I don't want to try and sort out the interpretive issues of how, precisely, he means to distinguish the two categories here, his discussion includes a set of (retrospectively) bizarre predictions about the longterm popularity of practitioners of the different styles. He says:
This also must be confessed, that the most durable, as well as justest fame, has been acquired by the easy philosophy, and that abstract reasoners seem hitherto to have enjoyed only a momentary reputation, from the caprice or ignorance of their own age, but have not been able to support their renown with more equitable posterity. It is easy for a profound philosopher to commit a mistake in his subtile reasonings; and one mistake is the necessary parent of another, while he pushes on his consequences, and is not deterred from embracing any conclusion, by its unusual appearance, or its contradiction to popular opinion. But a philosopher, who purposes only to represent the common sense of mankind in more beautiful and more engaging colours, if by accident he falls into error, goes no farther; but renewing his appeal to common sense, and the natural sentiments of the mind, returns into the right path, and secures himself from any dangerous illusions. The fame of Cicero flourishes at present; but that of Aristotle is utterly decayed. La Bruyere passes the seas, and still maintains his reputation: but the glory of Malebranche is confined to his own nation, and to his own age. And Addison, perhaps, will be read with pleasure, when Locke shall be entirely forgotten. (source)

From the perspective of contemporary academic philosophy in the United States, at least, these predictions are exactly backwards. I've had a decent amount of exposure to Aristotle's actual views, while the main thing I know about Cicero is that he also went by "Tully", and is thus a convenient example for illustrating Frege's Puzzle. While Malebranch wasn't a major focus of my early modern studies, he certainly got more attention that La Bruyere, and it is pretty clear that Locke has not been "entirely forgotten".

While I don't know how these figures reputations turned out outside of academia, or even outside of philosophy departments (and it is also possible that my experiences are not really representative), I always find this paragraph somewhat jarring as I settle in to read the Enquiry.

Wednesday, May 26, 2010

Simplicity Follow-Up

As I could have predicted, much of what I wrote in the previous post is not especially novel. From Alan Baker's SEP entry on Simplicity:
With respect to question (ii) ["What is the role of simplicity principles in different areas of inquiry?"], there is an important distinction to be made between two sorts of simplicity principle. Occam's Razor may be formulated as an epistemic principle: if theory T is simpler than theory T*, then it is rational (other things being equal) to believe T rather than T*. Or it may be formulated as a methodological principle: if T is simpler than T* then it is rational to adopt T as one's working theory for scientific purposes. These two conceptions of Occam's Razor require different sorts of justification in answer to question (iii)[Is there a rational justification for such simplicity principles?].

While this system of classifying ways of formulating Occam's Razor is pretty clearly in the same neighborhood as the contrast I was suggesting, I notice that Baker characterizes the methodological approach to Occam's Razor as facing the following practical challenge:
Justifying a methodological principle requires answering a pragmatic question: why does it make practical sense for theorists to adopt parsimonious theories? Most attention in the literature has centered on the first, epistemic question. It is easy to see how syntactic elegance in a theory can bring with it pragmatic advantages such as being more perspicuous, being easier to use and manipulate, and so on. But the case is more difficult to make for ontological parsimony. It is unclear what particular pragmatic disadvantages accrue to theories which postulate extra kinds of entities; indeed—as was mentioned in the previous section—such postulations can often bring with them striking syntactic simplification.

I quoted this passage because the sort of defense I gave for methodological simplicity was that it is easier to discover the limits of simpler theories, and (consequently) easier to learn how complex a theory must be in order to account for certain sorts of things. The methodology I described is not really the method of "adopting" a simple theory of practical purposes. It is the methodology of investigating the versatility of simple theories, without any further claim about epistemic or practical advantages of outright adopting that theory.

Baker's breakdown into epistemic and methodological seems to draw out the contrast between preferring simplicity because believing the simpler theory is a better way to arrive at true beliefs about the thing it is a theory of, versus preferring simplicity because proceeding as if the simpler theory is true is a better way to actually make predictions about and exert influence on the thing it is a theory of. My proposal, on the other hand, prefers simplicity because investigating simpler theories is a more efficient way to learn about the explanatory power of various sets of primitive resources. In itself, it carries no recommendation for believing the theory or for proceeding as if the theory were true.

Tuesday, May 25, 2010

Two Ways of Caring about Simplicity

I am not familiar with the literature on theoretical/ontological simplicity, so this post might be rehashing material that is well-worn among people who focus on such issues.

I think we can distinguish between two different ways in which a preference for simplicity can be manifested in philosophical inquiry. The first is in the role of adjudicating competing explanations. We have before us a set of rival theories, in competition as explanations of something or other, and we want to generate a ranking of theories from worst to best (presumably so that we may proceed to infer the best explanation). A ranking is going to be generated by scoring the theories in terms of some theoretical virtues (as in, the virtues possessed by theories). Caring about simplicity or parsimony can be manifested by making these rankings sensitive to the relative simplicity of the competing theories. As a first thought about this, it seems to me like simplicity isn't just going to be less important than, say, the virtue of capturing the data but that we will want a method of ranking that produces a lexical ordering where, for any two theories T1 and T2, if T1 is substantially better at capturing the data than T2, T1 outranks T2 regardless of their relative degrees of parsimony/simplicity. At the same time, as I said, I don't know the literature on this and it might be that something like noise in the data would weigh against such lexical orderings in favor of simply placing a lot more weight on data-capture than on simplicity. It is clear that there are a bunch of ways to actually institute the preference for simplicity as playing a role in ranking competing theories, and we can think about those as different versions of the view that simplicity matters in our evaluations of proposed explanations.

Contrast that way of valuing simplicity with a role it can play in guiding theory construction. We have some area of inquiry, like theory of mind, and maybe a general program or explanatory project we are keen to pursue, and we employ simplicity as a guide in our pursuit of the project. Here, caring about simplicity or parsimony can be manifested as a methodological commitment to be conservative with respect to the postulation of new primitive resources. As an example from the early modern period, philosophers offering reductive theories of mind (often in terms of a set of mental faculties/behaviors and a set of mental contents, like ideas) exhibited a wide range of different approaches to theory construction. Some were pretty liberal in introducing new primitive mental faculties or behaviors, while others tried to analyze all of our mental activities in terms of a quite small set of privileged faculties or behaviors.

It seems like the main advantages of adopting this sort of methodological preference for simplicity are: a) that, by severely constraining one's range of options for analyzing things, it consequently provides the theorist with increased direction for proposing analyses (roughly: there is a smaller search space of proposals using only the sparse resources), and b) that, by having fewer resources, it is easier to exhaust them, and thus, our investigations are likely to give us information about what the bare minimum of resources are for addressing a given issue (roughly: fewer resources means, in principle, less you can explain, and so you are more likely to find your explanatory needs outstripping your explanatory resources).

Incidentally, this is a big part of how I understand Hume's project in Book I of the Treatise. Hume's empiricism leads him to adopt hefty constraints on the nature and variety of ideas available on his theory, and Hume further limits himself by proposing only one fundamental type of cognitive activity (which can alternately be labeled conception if we are talking about the typing of cognitive states, or being present to the mind/understanding (with some or other degree of "force"/"vivacity") if we are speaking of the underlying analysis in terms of impressions and ideas. In the case of interpreting Hume, the (a) advantage outlined above produces a nice secondary benefit: it sufficiently narrows the range of viable interpretations of Hume's position on particular issues to inspire confidence about making progress on a number of interpretive debates.

Turning back to things not-directly-related-to-my-dissertation: It seems as though there are important differences between these two ways of implementing a preference for simplicity.

First, the former way assumes we have the array of competing theories already laid out in front of us, and we already know that we are selecting among adequate theories. On the other hand, the latter approach is recommended by, among other things, the high potential for generating inadequate theories. The attempt to rank theories looks like it should be supported by considerations having to do with a propensity for the simplest adequate theory to be true (or for simplicity of an adequate theory evidence of its truth), while the constraint on theory construction is supported by the utility of finding out the explanatory limits of a given set of resources.

Second, when using simplicity in ranking theories, it is important to note that just because T1 is the simplest adequate theory to explain P, and T2 is the simplest adequate theory to explain Q, it does not follow that T1&T2 is the simplest adequate theory to explain P&Q. It may be that T8 was pretty complex among the adequate explanations of P, and T12 was pretty complex among the adequate explanations of Q, but T12 and T8 overlap in such a way that T12&T8 is the simplest explanation of P&Q. So, the ranking of competing explanations of P (in isolation) may wind up being highly misleading about which theory of P we should prefer (all things considered). On the other hand, if T1 is not complex enough to account for P, it is also not complex enough to account for P&Q.

I am inclined to think the latter approach is safer in some sense, since it never delivers recommendations against the true view. I'll probably check out the SEP article on simplicity when I get a chance, but if you have particular recommendations for things worth reading on these topics, let me know.

Friday, May 14, 2010

Hume on Unreasonable Affections

On the question of whether passions can be unreasonable, Hume writes, famously:
[I]t is only in two senses, that any affection can be called unreasonable. First, When a passion, such as hope or fear, grief or joy, despair or security, is founded on the supposition or the existence of objects, which really do not exist. Secondly, When in exerting any passion in action, we chuse means insufficient for the designed end, and deceive ourselves in our judgment of causes and effects. Where a passion is neither founded on false suppositions, nor chuses means insufficient for the end, the understanding can neither justify nor condemn it.

On a natural reading of this passage, Hume has in mind cases like these:
False Supposition: Tom's fear of Casper the ghost. Given that there are no ghosts (and, in particular, that Casper the ghost does not exist), Tom's fear is founded on a false supposition (the supposition that Casper exists). Thus, Tom's fear can be called unreasonable.

Insufficient Means: Jane's decision to eat an apple (when motivated by her aversion to scurvy). Given that eating apples will not help one avoid scurvy, Jane's decision to eat the apple is founded on a false judgment about causes (of scurvy) and effects (of eating apples). Thus, Jane's decision (and/or action) can be called unreasonable.

Note that Hume's account of what makes for an "unreasonable" belief seems to be the following: A belief that P is unreasonable if and only if ~P. I'll come back to this point in a later post, but it is important to notice it here.

A natural criticism of Hume's position is that these cases don't seem to be cases of unreasonable emotions/decisions/actions. If anything, the false beliefs giving rise to Tom's fear and Jane's decision seem to help (rather than hinder) the reasonableness. What would be unreasonable, the thought goes, is for Tom to fear Caspar when he doesn't believe that Caspar exists (or for Jane to eat an apple as a way to avoid scurvy when she doesn't think apples prevent scurvy). To the first part of this criticism (the claim that the affections in these two cases are not unreasonable), I think Hume has room to maneuver. He even makes a point of articulating that "properly speaking" it is the judgments involved (and not the passions) which are unreasonable. So, what about the thought that there are these other cases, in which the passions are unreasonable?

Interestingly, Hume's framework leaves no room for such cases. Passions are secondary impressions (aka "impressions of reflection"), and thus, are responses to antecedent mental activity. In these cases, the passions can't be present in the absence of the relevant judgments. Setting aside the question of whether this is a desirable feature for Hume's mechanics of mind, it is, at least, an explanation of why Hume doesn't consider such cases: they are impossible, not irrational.