Why Do We Disagree So Much? Maybe the Space of Reasons is Extremely Populous

The point of this blog is to try and reconcile people with different perspectives, and that is bound up with analyzing the nature and sources of disagreement. I’ve written on the topic in Must Politics Be War? as well as in shorter essays, but I usually focus on epistemic reasons we disagree, such as limits of our cognition. But what if there is also a metaphysical explanation? What if we disagree so much not merely because of our cognitive limitations but due to the character of the space of reasons (specifically reasons to believe propositions)? What if there are unfathomably many reasons to believe things?

To see why this matters, suppose that the space of reasons to believe propositions is extremely populous. If so, then different people can detect wildly different samples of the space of reasons even if they are perfectly rational. And they will tend to emphasize reasons that they can locate from their position in the space of reasons. From each starting point, good inference can lead in an a staggering number of directions. If so, then disagreement is virtually certain even among perfectly rational and very informed agents. There are just too many reasons for belief for any normal rational agent to grasp. They are even less capable of unifying these reasons into doctrines, worldviews, and complex plans of action.

On analogy, imagine that it is your responsibility to chart the stars, and you’re really, really good at it. But then you learn that there are trillions and trillions of stars, and that other star charters start at different points in the galaxy. So you try to summarize the gargantuan number of stars with generalizations that look entirely reasonable from your point of view. You postulate constellations, or at least use them as heuristics to plot the relationship of stars to one another. But then you learn of star charters in other parts of the galaxy and that they see other stars, and so draw different connections between the stars. Should we expect star charters on different planets, and even star charters on the same planet, to generate the same constellations? Of course not. In fact, it’d be crazy to expect that they would without communicating with one another. The reason is that there are simply too many plausible ways to string things together.

What if disagreement is like that? How should we respond? Perhaps with wonder, humility, and a lot more charity.

1 Comment

  • Robin Hanson Posted December 11, 2019 10:41 am

    It is easy to explain why people disagree when they are unaware of each others’ opinions. The hard thing is to explain why people disagree AFTER they have learned that others disagree.

    (Btw, this interface has me type this comment in a VERY grey color font that is hard to distinguish from the white background.)

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