I was thinking about the common saying that “reasonable people can disagree”, especially with regard to politics. It’s one of the central tenets of being a “moderate”, and of maintaining a degree of civility in politics. But is it true?

It might be, but if so, what would that mean? After all, surely “reasonable people”, if they have all the same facts at their disposal concerning a specific policy, will reason the same way. That is to say, if they have what economists call “perfect information“, they would presumably come to the same conclusions.

Now, reasonable people might disagree if one (or both) of them did not have the facts, but that is no excuse. As soon as he got the facts, he would change his mind. Furthermore, if there were not enough information to formulate any conclusion, “reasonable people” would likely realize this, and would neither agree nor disagree about an issue; merely decide that at present they could not take a side.

There are two ways, as I see it, that reasonable people, with “perfect information” could disagree:

1. The self-interest case. If one reasonable person stands to lose from a policy, and another reasonable person stands to gain from it, they would presumably disagree about the policy if they were thinking purely in terms of maximizing their fortunes. (Of course, this opens up the can of worms about whether reasonable people would operate purely for self-interest.)
2. Political decisions are not based wholly in rational logic or intelligence. There are also other, more complicated considerations, having to do with upbringing, various events in a person’s life and other factors.

The first would mean we are governed only by our selfish desires. The second would mean that information and education are irrelevant, or only partially relevant, to political decision making, which would mean that even with “perfect information”, there would still be political parties fighting each other.

But feel free to disagree.