In this series of posts I am commenting on an article sent to me by a member of the studio audience. These are, in a sense, notes written in the margin as it were as I highlight passages in the article and explain my agreement or disagreement.
In my last post I suggested that it may be useful to distinguish two different senses in which we might say that a person’s actions are irrational.
One sense comes from comparing the action to an agent's current desires. An agent acts so as to fulfill the most and strongest of his current desires, given his beliefs. If those beliefs are irrational (if no rational person would believe such a thing under those circumstances), then we may also say that the act that springs (in part) from those beliefs are irrational.
The other sense comes from comparing the action to an agent’s current and future desires. Or, more precisely, it compares an agent’s actions to those desires that an agent has reason to have (desires that tend to fulfill current and future desires), not necessarily the desires that an agent does have. An agent may be irrational, in this sense, for failure to exercise not because he does have a desire to exercise (or does have desires that would cause him to exercise), but because h should have a desire to exercise. This is because a desire to exercise would tend to fulfill the agent's other present and future desires.
The charge of irrationality, in this sense, is an act of condemnation in the same way that a charge of immorality is. The difference is that charges of immorality are used to inhibit desires that tend to thwart the other desires regardless of whose they are; whereas charges of irrationality are used to inhibit desires that tend to thwart other (current and future) desires of the agent.
Why would we invent this language? Why would we adopt a set of linguistic conventions that aim at causing people to adopt desires that tend to fulfill the agent’s other desires, and inhibit those desires that tent to thwart the agent’s other desires?
Well, we certainly have reason to promote a set of social tools that make others interested in our welfare, just as they have reason to use those same social tools to promote in us an interest in their welfare. If I am interested in another person’s welfare then I am interested in removing those things that would cause harm to a person, just as I would have them adopt an interest in removing those things that threaten me. It means that I have a reason to promote in them desires that tend to fulfill their other desires, and to inhibit in them those desires that tend to thwart their other desires. And I have reason to have them do the same for me.
We have reason, then, for social conventions that praise those who acquire desires that tend to fulfill their other desires, and to thwart those desires that tend to inhibit other desires.
I am suggesting that if we look at the way that the charge of ‘irrationality’ is used, we will find this function as one of its many uses. Claims about another agent’s rationality and irrationality are used to mold desires in the same way that claims about another agent’s morality or immorality are used to mold desires. They simply mold these desires toward different ends.
This does not deny the fact that we also have an interest in the relationships between actions and the consequences of those actions on the one hand, and our current desires on the other. We have reason to adopt linguistic conventions for discussing these relationships as well. As it turns out, we find people using the terms 'should', 'ought', 'rational', and 'irrational' here as well.
Language is an invention and, like all human inventions, we have no particular reason to believe that it is flawless – that there are no parts of it that are unnecessarily vague or ambiguous. We have no reason to believe that it must be free of terms that lend themselves to ambiguity – where that ambiguity might cause confusion, even among philosophers.