Previously I argued that self-interest might be irrational, and hence undesirable, because of the possibility that one’s self-interested attitudes might rub off on the people around them. Let me assume that the kind of self-interest under consideration is a desire to maximize your total happiness (versus, say, maximizing your life expectancy). If this is the kind of self-interest that is under consideration then there is another reason to avoid it, specifically that people in general are unable to determine what will make them happy. (You can read an article about this phenomena here.)
The inability of people to predict what makes them happy was discovered by psychologists investigating self-interest with an eye to its connection with economics. And if their results are correct (and there is no reason to believe that they aren’t) then this is a good reason to see self-interest as irrational. Of course it doesn’t make self-interest irrational in the sense that it is self-defeating, it makes it irrational in the sense that it is a goal we can’t choose to accomplish or become closer to accomplishing in a systematic way. It is hard to give an example of another such goal that people might actually possess, since most of the time we are able to recognize that we can’t choose to make progress towards such goals, and thus think of them more as wishes. For example we might wish that money would fall out of the sky instead of rain, but there is nothing we can do to make this so. And thus we wouldn’t choose to live our lives trying to make money fall out of the sky, since it would be a wasted effort.
So perhaps happiness is better thought of as a wish. We might wish to be happy, but we can’t strive for it directly.* But maybe this is reading too much into what was shown. What was shown is that people can’t accurately predict what will make them happy. Perhaps by engaging in many different activities we can discover, by trial and error, which ones make us happy, and then use that knowledge to pursue happiness. This is certainly an idea, but there are some problems with it. Specifically it assumes that what makes us happy at one time will make us happy again at later times. And, even if it is the case that some activities make us happy fairly often, the strategy given here assumes that our preferences won’t change over longer periods of time. Even given these constraints we could still attempt to pursue happiness, but our strategy would be rather complicated, we would want to do the things we know make us happy, on average, but we would still have to take chances on things that might make us unhappy in order to hedge our bets against boredom or changes in our preferences.
These difficulties in pursuing happiness itself seem to highlight the futility of the enterprise. Much like a rat that has been trained to press a lever for a reward our behavior under the strategy outlined above begins to seem quite meaningless, which might lead to unhappiness, the very thing that we were trying to avoid. And if this is true than pursuing happiness really would be self-defeating, because the optimum strategy for pursuing happiness doesn’t make us all that happy, not happy enough to overshadow the fact that we aren’t accomplishing anything else.
A more intriguing possibility is to make happiness a meta-goal, specifically the goal we have in mind when we decide upon the goals we will be pursuing. For example, if you enjoy literature you might decide to write a book, because you think being an author might make you happy. The key is to not make happiness itself the goal. Writing the book itself may or may not make you happy, but that is not the point, the point is to be writing the book. And even if writing doesn’t make you happy perhaps meeting your goals will. In any case happiness seems like a dubious goal, since what seems to govern overall happiness is satisfaction with ones life, but satisfaction with ones life is not based on how happy you have been, but on how well you have met your other goals. It is difficult to wake up in the morning and try to be happy that day, but it is easy to wake up in the morning and try to accomplish some task, with the hope that accomplishing it will make you happy.
* Excluding, of course, drug use, which artificially induces happiness. Of course most people who say they want to be happy balk at the idea of using drugs to accomplish that goal. Which shows they really want something else, like success, and are hoping that end will make them happy.