What Are Desires?

A member of the studio audience asked a number of important questions.

Alonzo Fyfe states that a desire is a proposition that attaches a value to a state of affairs. This resonates with my intuitions very deeply - I remember first reading it and feeling a sudden clarity. It can go a long way to disabusing one of the supposed "fact/value" distinction that befogs minds that might otherwise be very perspicacious in ethical thinking. But as I consider this statement longer, I find that I don't really know how to interpret it. What does it mean to say that a desire "is" a proposition? Wouldn't it make more sense to say that a proposition *describes* a desire? Or that this desire is in some way analogous to a proposition? Or do you really mean that a desire is in some manner a linguistic object- that desires are composed of words? But then again, what else would a desire be composed of? Neurological impulses? Either way, assuming this is an empirical fact, how would we go about proving it, scientifically? Is it falsifiable? Is there an experiment we could perform to *prove* that a desire is a proposition that attaches a value to a state of affairs?

NOTE: I like questions from the studio audience. They force me to consider things I would not have thought of on my own.

First, a caveat. There is a lot of literature on the philosophy of mind. When I encountered this idea of propositional attitudes I realized that if I were to study these issues, I would have no time to do ethics. Therefor, I decided that I would have to trust the philosophical consensus on such matters, rather than participate in that particular debate.

Second, a caveat to the caveat. Almost all of that philosophical work concerns beliefs. When it comes to the philosophical study of desires, there is little to go on. In fact, the previous two posts focused on a case where theorists put a great deal of thought into beliefs. They then waved their hands in the direction of desires and said, “The same is true over there.” My response in those two posts was, “No, it’s not the same over there, and I can prove it.”

Now, let’s see if I have learned anything in the past few years. I think I can now give a better definition of what a desire is.

A desire is a brain state that assigns a motivational value to a proposition being true.

Let me say a few words about the parts.

Desire is a brain state: When we talk about beliefs and desires, we are talking about the structure of the brain. The claim, “Jim prefers chocolate to vanilla” is a statement about how the matter between Jim’s ears is organized. Such a hypothesis can be verified or falsified by looking at Jim’s intentional actions.

A proposition being true. This is more precise than talking about “a state of affairs”. If a desire assigns a truth value to a whole state of affairs, and that state of affairs changes (states of affairs are constantly changing), how does that relate state of affairs changes to the desire? A change is relevant (relative to that specific desire) only insofar as it is relevant to the proposition that is the object of the desire being true or false.

Motivational value: Clearly, assigning a value to something is insufficient to motivate action. Assigning the value “less than 80kg” to “my weight” does not provide a reason for action. However, assigning a motivational value (a to-be-ness) to the proposition “my weight is less than 80kg” being true gives me a reason to realize a state in which my weight is less than 80kg. However, I can also have a desire that I be eating another slice of that chocolate cake and, if the motivational value is higher, then my desire that my weight is below 80kg gets thwarted.

So, that is a desire, as I currently understand it.

So, now on to the questions:

What does it mean to say that a desire "is" a proposition?

It isn’t. It is a brain state.

Wouldn't it make more sense to say that a proposition *describes* a desire?

Try this: A proposition being true is the object of a desire. The desire is a gun. The proposition being true is the target.

Or do you really mean that a desire is in some manner a linguistic object- that desires are composed of words?

The propositions that are the objects of desires (and beliefs) cannot be words. Animals have propositional attitudes (an aversion to pain), even though it has no words.

What an animal does have is concepts. A dog has a concept of a ball. It also has a concept that refers to the same thing we would refer to by the word "owner". The dog, of course, does not have a concept of "owner" but a concept that refers to the same person. This happens in the same way that the concept of "Clark Kent" is different from the concept of "Superman" even though they both refer to the same person.

We can form relationships among concepts. I can relate the concept of "I" to "weigh less than 80kg". An example of a belief is a relationship between "I", "weigh less than 80kg" and "is true". An example of a desire is a relationship between "I", "weigh less than 80kg" and "is to be made or kept true".

I want to repeat, concepts came before words. A dog can relate the concepts of "ball", "bring back to owner", and "to be made true" without having any words.

But then again, what else would a desire be composed of? Neurological impulses?

There are probably over a hundred books and thousands of articles written on this subject. I tend to favor a view called "functionalism" which states that a desire is an arrangement of matter that relates input to output, where the output is intentional action. It is like a line on a computer program that says, "Assign to the relationship of concepts 'I' and 'weigh less than 80kg' the motivational value (strength) M"

Is there an experiment we could perform to *prove* that a desire is a proposition that attaches a value to a state of affairs?

The theory being presented here would be a metatheory - like the theory of evolution. We cannot test the theory of evolution directly. Instead, we test it by its ability to fruitfully generate other claims that can be tested - e.g., claims about the relationships between fossils and the ages of rock layers. Evolution produces a lot of testable hypothesis.

We are constantly using belief-desire theory to create hypothesi that allow us to predict and explain the behavior of other people. The ability to be able to explain, predict, and to modify the behavior of others (this being particularly important for desirism as a moral theory) by using belief-desire theory (which all of us do, all the time) is the best evidence of its truth. If the theory ever becomes replaced, it will need to be replaced by a different theory that allows us to do an even better job of explaining, predicting, and modifying behaviors.

Until people come up with a better way to explain, predict, and modify behaviors, we need to stick with the best theory we currently have. Even when people knew that there were problems with Newton's theories of motion, for 300 years, until Einstein came along, they had no choice but to continue to use Newtonian physics. Even after Einsteinian physics came along, it was of no use for every-day purposes. We still use Newtonian physics, since it is still good enough (and simple enough) of all practical purposes.