Desires

Desires, along with beliefs, are the proximate causes of intentional action. When you ask why somebody did something, you expect an answer that provides you with the relevant beliefs and desires that explain that action. Not only must it explain that specific action, but it must make that action consistent with other actions that the agent has performed and be able to predict potential future actions.

"Why did you choose to invest in that particular mutual fund."

The answer may involve wanting a high rate of return and believing that the mutual fund will provide it. The answer might include some interest in social responsibility. Perhaps a family member works for the company and the investor wanted to support her, or the investor values investing in developing economies and believes that the mutual fund focuses on those types of investments.

It is important to note that beliefs and desires explain and predict observable events in the real world. While there is some dispute about the merits of this form of explanation; in our every-day world, we currently have nothing better.

So, what are these entities that explain intentional action?

Beliefs and desires are mental states. They are properties of the mind-brain - physical properties of physical objects in the physical universe.

Beliefs and desires are functional properties - properties that describe what is going on (or can go on) within an object. In this, the mind-brain is much like a computer, storing data (beliefs) that might or might not be true, assigning value to certain states, and using that data and those values to determine output (behavior).

Beliefs and desires are known as "propositional attitudes". This means that they describe attitudes towards propositions.

A proposition, in turn, is the meaning component of a sentence. It is a statement capable of being true or false. “Jenny is visiting her mother in Iowa” is a proposition. It is a statement. It might be true. It might be false. "Jenny is in Iowa visiting her mother" is a different sentence, but it is the same proposition. It says the same thing.

A belief is the attitude that a proposition is true. A belief can be expressed in the form, "A believes that P", where "P" is some proposition, A is the agent who believes that P, and "believes" is the attitude that A has towards the proposition P. A believes that P means that A holds the proposition "P" to be true - an accurate description of the world. A person who believes that P will plan his actions for a universe in which "P" is true. If "P" happens to be false, this will usually have an adverse effect on the agent's success.

So, if Ivan believe that Jenny is in Iowa visiting her mother, and Ivan desires to talk to Jenny, and Ivan knows her mother's phone number, then Ivan should conclude that Ivan can reach Jenny by calling that number and Ivan has a motivating reason to call that number. If that belief is false, Ivan is wasting his time calling that number.

A desire is a motivational drive to make a proposition true or to keep the proposition true.

If Ivan wants Jenny to visit her mother in Iowa, this gives him a motivating reason to act to make the proposition, "Jenny is visiting her mother in Iowa" true. Ivan may try to persuade Jenny to visit her mother. Ivan may purchase an airplane ticket for her. What Ivan will be looking for is an action - given his beliefs - that is likely to make it true that Jenny is visiting her mother.

It is important to stress here that what matters is the objective satisfaction of a desire - creating a state where the proposition that is desired is objectively true in the real world. (Earlier writings on desirism used the term "desire fulfillment". However, the academic community appears to be settling on the phrase "objective desire satisfaction".)

This is to be understood in contrast with "subjective desire satisfaction" - which is the (potentially false) belief that a desired proposition is true.

A parent may believe that his child is safe at a friend's house. At that moment, unknown to the parent, she may be the victim of a violent attack. The parent's desire that their child is safe is subjectively satisfied (he believes it is true) but not objectively satisfied (true in fact). Of the two, intentional action aims for objective satisfaction (making a proposition true in fact), not subjective satisfaction (making oneself believe that it is true).

Each person is motivated only by his or her own desires (and beliefs).

This is a truth that egoists note, but that they do not understand. Egoists note that agents always act solely on their own desires. They then confuse this with the claim that everybody acts for their own benefit. When challenged by a case in which a person acts to benefit others, they will answer, "She is still doing what she wants." This is true. However, if what she desires is the well-being of another person, this is not egoistic selfishness. It is the very definition of altruism.

Even if it were possible for one agent's (Andrez's) desires to motivate the actions of another person (Ben) - for Andrez's desires to cause Ben's limbs to move and to realize states of affairs that Andrez is motivated to bring about – those actions would be Andrez's actions, not Ben's. An action can not, at the same time, be Andrez's action and come from Ben's mental states. If those actions come from Andrez's mental states (or the degree to which they come from Andrez's mental states), they belong to Andrez, not to Ben.

A mind control device that would allow one peson to take over the body of another and commit a crime would not make the second person guilty of that crime. Because the crime did not spring from the beliefs and desires of the second person, the second person is not morally responsible for those actions. The culpable agent, in this case, would be the one who did the controlling - the person whose beliefs and desires actually produced the action.

When we morally evaluate an action, we are actually evaluating the mental states behind that action - and the person to whom those mental states belong.