Occasionally there is some odd comment here or there on this site alluding to “rational choice” models. Now almost nobody in economics uses this phrase, because you don’t need a word to describe what everyone is doing. Yet rationality seems to get some non-economists excited. Why?
The most likely candidate is definitional confusion. Economists make lots of assumptions (so, by the way, do all humans) which may or may not be useful or correct. But most of these are not the infamous “rationality”.
The definition of rationality is a very dull thing indeed, surely nothing worthy of the excitement it generates. A rational agent is one that, for any choice, prefers one of the options or is indifferent. And these preferences must be transitive, so that if A is preferred to B and B to C then A is preferred to C. Lastly, by “preferred” I certainly don’t mean what will make them happy or anything like that, I just mean that that is the one they actually pick if offered a choice.
A model with these characteristics is “rational choice”. There are lots of other assumptions one may or may not wish to make, but we’re done with rationality and on to other, more controversial things, like that people have perfect information or that what one prefers is what makes one happy. All of these additional things are open for debate, but no matter the debate’s resolution, the model is still a rational choice model.
Now I ask you. Why would you ever trust a model of human behavior that relied on agents with incomplete or non-transitive preferences to get its results? Truly that would be a thing worthy of derision.