Admittedly, in many cases this argument is a good one. It probably makes no sense to spend a lot of energy optimizing the choice of lunch. As for myself, I’ll just pick something that’s tasty enough and healthy enough, without worrying whether there might be a better alternative. In fact, there is considerable evidence that this kind of behavior is better in the long run, when small choices are being considered. For a thorough argument, see for example Barry Schwartz’s book The Paradox of Choice.
But there is a fatal flaw in the argument, which renders it unsuitable for the assumed role of a magic bullet. The argument assumes that all decisions are independent of each other. If this were true, then the differences of rationality and good enough choices – assuming they’re small – don’t build up to a very large extent. A sum of small differences is still a small number. Unfortunately, the independence assumption is not warranted. For example, consider the case of choosing a job. It is plain that this choice has a heavy effect on your future choices concerning family life, work-life balance and career development. An optimal choice in this respect will maximize the opportunities you have in the future, and enable better decision opportunities then.
Rationality has a cumulative force. A given rational decision may not be very much better than a less rational one, yet it leads to a new decision situation somewhat different from that the other would have produced; and in this new decision situation a further rational action produces its results and leads to still another decision situation. Over extended time, small differences in rationality compound to produce very different results.
- - Robert Nozick (1993): Nature of Rationality, p. 175
The habitual behavior is in some way giving hope. I know from the literature – and even more so from personal experience – that we cannot change all our ways at once. Trying to eat better, exercise more, facebook less and read more books at the same time is a plan that’s doomed from the start. There’s just too much to remember, too much to focus on. The same goes for better thinking: it doesn’t make any sense to expect that we’ll be able to optimize all our decisions as soon as we decide to try. No – we’ll still get tired, lose our focus and tons of other things that prevent a good, reflective decision. But by cultivating the habit of rationality, we slowly but surely go towards better decision making – one decision at a time. And after a while, we hopefully notice that the habit has become almost automatic, and making good decisions is not so hard anymore.
And that’s when we’ll really start reaping the benefits from the fact that rationality is cumulative.