Sunday, June 24, 2018

On Desire 2018. Part 50: Neo-Humean Theories of Desire and the Brain

In discussing Timoty Schroeder's article on the neurobiology of intentional action (Schroeder, Timothy, (2017), “Empirical Evidence against a Cognitivist Theory of Desire and Action", In Deonna J. & Lauria F. (eds). The Nature of Desire. Oxford University Press), I have so far (1) presented his summary of evidence regarding the neurobiology of intentional action, and (2) used this information in presenting his arguments against cognitivist theories of desire.

The next thing to do is to look at what Schroeder says this information has to say about neo-Humean theories of desire.

The theory that I defend is something of an odd duck. Typically, theories of desire are divided into two camps, evaluationist (desires are evaluations that something is good or ought to be the case) and dispositional (theories of desire are statements about how people are disposed to act). So, if there are problems with evaluationist theories, then that leaves dispositional theories. Schroeder has so far used his empirical evidence against evaluationist theories of desire. This leaves the dispositional or, what Schroeder calls, "neo-Humean" theories of desire.

On this simplest approach, one holds that desires characteristically dispose us to perform actions that seem likely to bring about (or make progress towards) the ends we intrinsically desire.

The theory that I support is an evaluationist theory. However, a "desire that P" is not a belief or judgment that P has value. It is an assignment of value to "P" being true. It requires no belief or judgment, so it does not require a pathway through the parts of the brain associated with beliefs and judgments. An action, such as writing a blog posting on desires, does look at the propositions P that are believed and judged to be true in that state of affairs, but the assignment of a value to those propositions being true can all be done behind the scenes without any contribution from beliefs or judgments. The weighing of the value of those propositions being true against the value of different propositions being true if I were, for example, to go fix myself something to eat, keeps me at the computer writing this blog post.

Of course, assigning a value to a proposition being true also determines the motivational force of making or keeping that proposition true, and so disposes one to act to the degree that one can find a relevant action to perform. However, the action is caused by the desire. The assignment of a value to a state of affairs is causally prior to action and is the reason for the action, when there is action.

With this distinction in mind, let us look at what Schroeder says about the empirical data with respect to neo-Humean dispositional theory and see if we can apply it to the assignment theory of desire.

As it turns out, Schroeder's interpretation of the causal map does not actually involve dispositions to act. It is more consistent with the assignment of value to "representations of perceivable or conceivable contents".

If intrinsic desires are, or are realized be, or subvene on, perceptual and conceptual representations that are connected in the right way to the reward system (such that their contents are constituted as rewards), then instrinsic desires will turn out to have the properties and play the roles attributed to them by the simplest form of neo-Humeanism.

So, we are looking at "perceptual or conceptual representations" (think of these as "perceives that P" or "believes that P"), where their content (P being true) are constituted as rewards (are assigned a value V, which is the strength of the reason to make or keep P true), then they will generate dispositions to act to make or keep P true.

Desires, as Schroeder describes them, are not mere dispositions to act. They are assignments of value to propositions being made or kept true that provide agents with reasons to act, if a viable act can be found. And this "if a viable act can be found" can, perhaps, be related to the acts queued up as a result of the belief/perceptual portion of the brain looking for permission to continue.

I am, so far, quite pleased about the way that the evidence Schroeder presents on the biology of intentional action fits in with the assignment theory of desire used in desirism. However, the book The Nature of Desire contains a second article discussing the empirical evidence. I will be examining that next.

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