Online research in philosophy

In this paper I will argue against the Humean theory of motivation, or “conativism” which claims that all actions are ultimately generated by desires. Conativism is supported by (1) a behavioral analysis of desire as a disposition to act in certain ways, and (2) the difference between belief and desire in terms of their different “direction of fi t” with the world. I will show that this behavioral account of desire cannot provide an adequate explanation of action. Mere disposition to act (what I call “wanting”) does not explain why the agent acts; insofar as it explains the action desire is a feeling. I will then argue against the direction of fit argument by showing that beliefs about what we ought to do have both directions of fit—the belief has one direction of fit, and the content of the belief (the ought-clause) has the opposite direction of fit.

This paper provides new foundations for Bayesian Decision Theory based on a representation theorem for preferences defined on a set of prospects containing both factual and conditional possibilities. This use of a rich set of prospects not only provides a framework within which the main theoretical claims of Savage, Ramsey, Jeffrey and others can be stated and compared, but also allows for the postulation of an extended Bayesian model of rational belief and desire from which they can be derived as special cases. The main theorem of the paper establishes the existence of a such a Bayesian representation of preferences over conditional prospects, i.e. the existence of a pair of real-valued functions respectively measuring the agent’s degrees of belief and desire and which satisfy the postulated rationality conditions on partial belief and desire. The representation of partial belief is shown to be unique and that of partial desire, unique up to a linear transformation.

Granted that desire is always present in the genesis of human action, is it something on the presence of which the agent always reflects? I may act on a belief without coming to recognize that I have the belief. Can I act on a desire without recognizing that I have the desire? In particular, can the desire have a motivational presence in my decision making, figuring in the background, as it were, without appearing in the content of my deliberation, in the foreground? We argue, perhaps unsurprisingly, that yes, desire can figure in the background without figuring in the foreground: we call this the strict background view of desire. But we then show, and this is where the surprise comes, that the strict background view of desire has significant implications for contemporary moral philosophy.

Rationalizations of deliberation often make reference to two kinds of mental state, which we call belief and desire. It is worth asking whether these kinds are necessarily distinct, or whether it might be possible to construe desire as belief of a certain sort — belief, say, about what would be good. An expected value theory formalizes our notions of belief and desire, treating each as a matter of degree. In this context the thesis that desire is belief might amount to the claim that the degree to which an agent desires any proposition A equals the degree to which the agent believes the proposition that A would be good. We shall write this latter proposition ‘A◦’ (pronounced ‘A halo’). The Desire-as-Belief Thesis states, then, that to each proposition A there corresponds another proposition A◦, where the probability of A◦ equals the expected value of A.

Bryne & H´ajek (1997) argue that Lewis’s (1988; 1996) objections to identifying desire with belief do not go through if our notion of desire is ‘causalized’ (characterized by causal, rather than evidential, decision theory). I argue that versions of the argument go through on certain assumptions about the formulation of decision theory. There is one version of causal decision theory where the original arguments cannot be formulated—the ‘imaging’ formulation that Joyce (1999) advocates. But I argue this formulation is independently objectionable. If we want to maintain the desire as belief thesis, there’s no shortcut through causalization.