|
The only place a statement like "rational people behave in predictable ways" isn't a fallacy is in an econ textbook. This is because in an economic textbook it's a tautology: Predictable Behavior -> Rationality and Rationality -> Predictable Behavior.
As Ace used the phrase (Governmental revenue forecasting is easy because rational people are predictable) it's definitely not true. On an individual level it doesn't apply because people acting in a completely rational capacity do unpredictable things all of the time. It is only in hindsight that we attach the rational label to their motivations. Even then, the act of attaching the rational label to a person's thoughts is highly subjective. On a more macro scale, the phrase doesn't apply, because then you're looking at the emergent properties of a complex system, which are defined by the system's individual components acting in concert and which are not necessarily all that predictable.
Even if it weren't a fallacy, the idea that "rational people behave in predictable ways" is fairly meaningless as anything other than a guiding principle, because the type of awareness and computing power required to predict anything of economic significance with any amount of certainty doesn't exist.
|