Not that hard to argue this, really. Consider that you have desires, simple things like, “I want to start a family,” “I want to have a successful career that I enjoy,” “I want to enjoy the company of friends and family.” We all have such desires, things that we want to bring about. So, the question is, how do we best achieve these goals?

There is where being rational comes in. Being rational allows us to objectively examine the evidence to determine which actions will be most likely to bring about that which we desire. It also allows us to examine conflicting desires, weigh them against one another, and determine which we really do want (e.g. I want to buy a fast new computer, and I like AMD’s processors, but Intel’s are faster right now).

So yeah, if you have any desires at all, and you want to bring those desires about, then you should be as rational as possible in bringing about your desires.

Why? The circular answer is nice:

Definition of the rational strategy: The optimal strategy to reach the own aims.

Why should I be rational? To reach the own aims.

Why should I reach my own aims? You should not. Its your choice. But I think you want it.

The argument economists have is that they don’t need to worry about such things because we live in an age of plenty, so physical limitations don’t really matter.

Unless I’m wrong, economists seem to assume that human wants and desires will allow them to overcome physical limitations via technological innovations. The fact that a drought can wipe out an agricultural crop can be overcome by say, mining groundwater or piping water from a large distant river.

However, this assumes a never-ending supply of energy and a never-ending supply of arable land for an ever-increasing human population. Such assumptions are hardly justified.

As proof of this, the econometric models used by many economists to justify NAFTA predicted a net rise in pay on either side of the US-Mexico border due to increased efficiencies on both sides. The actual result was the opposite, and no economist has ever been able to explain why their models failed so miserably – in fact, they don’t even talk about it.

I don’t know. Should you? You’re asking the wrong question.

Q: Can you give a nontrivial non-circular answer to the question: “Why should I be Rational?”