Two Approaches to Instrumental Rationality and Belief Consistency

Article excerpt

IN SPEAKING OF INSTRUMENTAL RATIONALITY, philosophers usually have in mind the rational requirement of taking the necessary means to our ends. A central question of this paper is how this rational requirement is related to the rational requirement to hold consistent beliefs. I will primarily be concerned with evaluating two ways of understanding the relationship between instrumental rationality and belief consistency. First, I will consider R. Jay Wallace's view that instrumental rationality just consists in having consistent beliefs. (1) According to this view, if you are an instrumentally irrational agent, you have a set of inconsistent beliefs. Wallace thinks that this allows for the normativity of instrumental rationality to be traced to the independent rational requirement to hold consistent beliefs. Second, I will consider the view, proposed by John Broome, that the requirements of instrumental rationality and belief consistency are similar in structure. (2) Broome does not attempt to reduce instrumental rationality to belief consistency, but suggests that the two are structurally similar in that the correctness of both instrumental reasoning and reasoning leading to consistent beliefs is explained by appealing to the logical relations of propositions that are either intended or believed. Despite the differences, both Broome and Wallace do share some common assumptions in that they both aim to provide an account of instrumental rationality according to which instrumental rationality involves a restriction on a certain combination of attitudes--for Broome, a certain combination of intentions (along with a belief about the necessary means) and, for Wallace, a certain combination of beliefs.

I argue that Broome's approach is preferable to Wallace's since there are three objections to Wallace's account, which I present in the first section below, that Broome can avoid. I believe it is better to think of instrumental rationality as involving a restriction on a certain combination of intentions than a restriction on a certain combination of beliefs.

However, in the second section, I go on to note that Broome's account is problematic since it does not seem to be the case that having consistent intentions suffices to make an agent instrumentally rational. I argue that an agent with consistent intentions could still be instrumentally irrational by failing in his instrumental reasoning. So, if we say that instrumental rationality consists in having consistent intentions, then we haven't told the whole story of instrumental rationality. In the third section, I aim to show that this is an important conclusion because it shows that Broome's conception of instrumental rationality as a restriction on a certain combination of intentions is actually vulnerable to a critique which both he and Wallace present against different parts of Christine Korsgaard's conception of instrumental rationality. Both Broome and Wallace point to certain instances in which an agent can engage in instrumental reasoning (correctly or incorrectly) and suggest that Korsgaard's account needs to be expanded to accommodate these instances of instrumental reasoning. But I point out that it is possible for an agent to engage in instrumental reasoning (correctly or incorrectly) even when his intentions are consistent. So, by the same reasoning which Broome and Wallace use against Korsgaard, Broome's account of instrumental rationality needs to be expanded to accommodate these instances of instrumental reasoning.

In short, I argue that while it is better to think of instrumental rationality as involving a requirement to hold consistent intentions than a requirement to hold consistent beliefs, we should not think that such a requirement explains the whole of instrumental rationality.

1. Instrumental Rationality as Belief Consistency

On Wallace's view, the normative force of instrumental rationality is accounted for in terms of the inconsistency of the beliefs held by the instrumentally irrational agent. …