When we talk about Rationality, what are we talking about?

Rationality seems to be the factor that perplexes the whole discussion. According to Merriam-Webster, rationality is the quality or state of being reasonable. So being rational is being reasonable. But the first common sense Sen refused when he started his book is that assuming human behavior with rational behavior. But since assuming human behavior with any particular type of irrationality is more problematic, people accept the rationality ideal because it provides a pattern. Patterning is essential to any field of studies. Without patterning, principles and theories would no longer work, losing its value to be predictive.

So to find rationality is to find the underlying pattern that guide the human behavior. Sen talked about both rationality as consistency, concluding that it is not an adequate condition, and rationality as self-interest, admitting its necessity but pondering its sufficiency. Rationality as self-interest is derived by most economists who emphasize the engineering origin of economics. Note that Smith would derive prudence instead of self-interest from the emphasis of this origin. Prudence seems to be the rationality that generalizes and summarizes all kinds of self-interest. If going afar from the ethics origin, according to Smith, sympathy would be another part of rationality. Rationality as sympathy, according to Sen and Frank, influences human behavior as effective as self-interest, but it is less explored by the economists, as economics becomes more and more math-based.

Over the last 30 years, behavioral economics becomes popular. But it is largely debated of its usefulness because the patterning it yields is not as predictive as traditional economic theory. Psychological, social, and emotional factors do not foretell as well. Interpreting from another perspective, can we just say that most people share the same attitude towards self-interest, but that their views on sympathy are more at odds? The strength of sympathy and affection is weakened by the lower predictability of the behavioral economics theories. Further, emotional bond is harder to quantify than legal bond, and its violation is harder to penalize. According to Frank, people with less sympathy will defect more often than those with more. But Frank does not provide how people can foresee and constrain the defectors. Even though he believes that people are sophisticated and we are able to tell those unfeeling people – especially strangers – from involuntary facial expression and body language, intuition is not legally protected. Without certain enforcement and punishment, defectors could be as rampant as they would if they are only constrained by emotional bond. I think the only solution to sustain cooperation is through people’s reputation. As Frank said, people care about the costs and benefits in the future, even more than how much they care about today. Reputation sustains the self-interest in the future. At the end, self-interest still dominates rationality. I would love to have sympathy becomes part of rationality as well, but philosophers and economists need to work more carefully.