[Klockan]

> In economic theory, rationality is defined only as: when faced with a decision over many choices, the actor always chooses the choice they value most, according to their own "utility function".

That definition is correct but it isn't useful which is why it is never used in models. In the end we need to assume that the actors values something and that assumption will have a huge impact for any mathematical model. So the point is that since our assumptions about what people value can have so large consequences the maths doesn't really matter, it all comes down to people choosing their assumptions such that the result verifies their own beliefs.