Is it irrational to be selfish or evil? You might think not, as people typically separate ethics and rationality, but I think this is a mistake. From genocidal tyrants to inconsiderate neighbours, wrongdoers are not just mean and nasty, they’re also making intellectual errors. They fail to draw the conclusions and perform the actions that they rationally should.
This might sound surprising. It’s widely assumed that the only form of rationality is instrumental rationality – that is, taking effective means to achieving your desired ends, whatever they might be. If you want to be rich, and could achieve this by exploiting other people who you don’t care about, then the “rational” thing to do is exploit them – or so economists and game theorists would have us believe. They assume that there is no possible basis for assessing ultimate goals. The fact that you care more about money than people might make you mean, but it’s no failure of rationality on your part.
Although one can see why this claim might appeal to economists (ha, sorry, cheap shot), we need not accept such an impoverished conception of rationality. We can go beyond mere means-ends reasoning, and assess a set of values for internal consistency and coherence. That is, we can assess a set of ‘ends’ as being more or less rational to desire. We are not limited to merely assessing the efficiency of various ‘means’ to achieving them.
For example, we tend to consider it irrational for an agent to disregard their future interests. Suppose Larry only cares about what will happen to him during the present year, and has no concern whatsoever for how he fares after that. He might get into huge debt, seeking immediate gratification without regard for the costs he’ll suffer later. Wouldn’t you consider such behaviour to be irrational? But note that Larry exhibits no flaw in his means-ends reasoning: he’s successfully achieving precisely what he wants; the problem is that he wants the wrong things. Larry might not care about his long-term interests, but he ought to, and a more reasonable person would.
We can bring out the inconsistency in Larry’s desires by noticing that he draws arbitrary distinctions. He cares about what happens to him on New Year’s Eve of this year, but not what happens the day after. But there is no relevant difference between these two cases that would justify his taking such different attitudes towards them. If he cares about one then he rationally ought to care about the other, for they are similar in all relevant respects.
So we see that rationality requires us to treat like cases alike, and not to draw arbitrary distinctions. We can apply this to morality by examining the distinctions we draw between people that we think do or don’t “matter”. All of us think at least some people matter: at a minimum, our selves, friends, and family. But sometimes we disregard others’ interests. The most rationally coherent value set would contain a general principle explaining why we care about the welfare of the first group of people but not the others. Otherwise we are just like Larry, inconsistently caring about some cases but not others, when there is no principled basis for distinguishing between the two.
The question now arises: is there such any such principle? We might illuminate this by considering a visual metaphor. Imagine yourself at the centre of the universe (too easy!), with everybody else arranged around you based on how similar you are according to the relevant criteria, whatever that might turn out to be. So all the “like cases” are clumped around close to you, with people differing more and more as they get more distant.
Now imagine that you hold a powerful light above your head – representing your moral consideration – so that the light reaches everyone that matters to you. The light is clearly going to touch many other people too, since they will be relevantly similar to yourself or people you care about, and thus will be positioned nearby and within the light’s reach. What this shows is that you rationally ought to think that the welfare of these others matters too. You should take their interests into moral consideration.
That’s not to say that you must care about all people equally. The fact that someone is your close friend gives you reason to care more about them than a mere acquaintance. There are some relevant differences, and they will eventually add up. Returning to the ‘light’ metaphor, we can note that the light will get progressively dimmer the further away it extends. Those that are most important according to the relevant criteria will be near you in the centre, thus receiving the most light – the strongest weight in your moral consideration. This will get weaker as minor relevant differences build up into more and more significant distinctions as people get “further away” from you in our imagined ordering.
Perhaps you ought to have most concern for friends and family, a bit less for acquaintances and neighbours, and again for fellow citizens, then foreigners, etc. At each step you can identify some relevant differences, but none so significant as to justify a clear-cut distinction of saying that the first person matters and the second one doesn’t matter at all. To draw such a distinction would be arbitrary, and so leave you open to rational criticism for your inconsistency.
We’re now in a position to see why immorality is irrational. Ethics is essentially a matter of taking others’ interests into account. It is wrong to cause undue harm to another person. Is it also irrational? Given that we already take some people’s interests into account, consistency requires that we expand our sphere of moral consideration to encompass others that are relevantly similar. In order to avoid drawing arbitrary distinctions, we must recognize that other people matter too. In other words, yes, we are rationally required to be ethical. Contrary to common assumptions, the evil man is not just nasty, he’s downright irrational.