Sen believes people can change the world through rational choices. This requires a framework to evaluate options, institutions to further goals and values, and behavioral norms that fit these ends. Yet, many skeptics challenge the possibility of rationally shaping the world in this way. Some question the possibility of society agreeing on a common evaluative framework. Kenneth Arrow has mathematically demonstrated this in his “impossibility theorem” that a ranked-choice voting system—in which people decide between more than two options by ranking preferences—always has the possibility of leading to inconsistent outcomes with decreased happiness. To simplify, the preference of the majority may come at the expense of the minority, like two people deciding to split a cake between themselves while giving nothing to the third. However, Arrow’s theorem doesn’t account for decision-making that incorporates a different informational base beyond simple ranked preferences—that is, concerns about poverty and equality. More generally, diverse opinions can be overcome by gradually building social consensus. Many rational decisions can be implemented even with imperfect consensus.

Other skeptics point to the pervasive influence of unintended consequences. Sen says that people have learned from failures and accomplished many things they did intend, such as improving literacy. China’s economic and social planning has spawned some negative unintended and unforeseen consequences, such as a rise in the deaths of female children; but the fact that they did not foresee these consequences does not mean they could not have anticipated them.