A key assumption in economics is the assumption of rationality on the part of economic actors. This assumptions tends to be controversial, especially among non-economists. However, I want to argue that the nature of the assumption has implications beyond just the economic model implications. Implications that are applicable to all sciences, not just economics.
Let’s first begin by defining what we mean by rationality. All rationality means is that actors move forward toward a goal based on the information they have. Since that information is not perfect, their actions may not be perfect in achieving that goal, but generally speaking people, once they make a decision, will move purposely. For example, a hungry person would rationally move toward trying to eat: buying food, stealing food, forging, etc. All of these are rational actions.
What can this assumption mean beyond economic models? I think, from a scientific point of view (or, at least, a social scientific point of view), the rationality assumption forces humility on the part of the analyst. If we assume the actor is rational, then we look at any action he takes as purposeful, even if we ourselves wouldn’t take such an action. In short, it forces us to ask the question “why does this outcome occur?” It forces us to avoid, or at least question, to urge to direct another through policy or “nudges.” If Jones takes an action, it is likely because Jones views that action as the best of the available alternatives to his best knowledge.
In the social sciences (and in this, I am including political science), i think the rationality assumption provides both awesome insight and forces humility on the part of the analyst, a valuable trait to remaining unbiased and avoiding what Hayek called “the pretense of knowledge.”