Wednesday, August 20, 2014

Experimental Testing of the Rawlsian Difference Principle

I have often argued on this blog that political philosophy is ultimately an empirical science that makes falsifiable claims about human nature and human history.  In arguing for Darwinian natural right, I am making falsifiable claims about Darwinian moral psychology that can be tested.

One can see this empirical falsifiability of political philosophy in John Rawls's Theory of Justice.  He makes a general claim that our capacity for justice requires a natural sense of justice or moral nature, which is comparable to what Noam Chomsky has identified in linguistics as the instinctive universal grammar that makes the acquisition of language possible (46-53).  He also makes a specific claim that under the conditions of the "original position" that are designed to ensure impartiality, human beings would unanimously choose certain principles of justice, including the "difference principle" that social and economic inequalities are justified only when they maximize the benefits for those who are worst off (60, 302). 

There is, I believe, some empirical evidence supporting Rawls's general claim for an evolved innate moral grammar or moral sense.  I will write about that in my next post.  His specific claim for the difference principle, however, has been empirically falsified.

Although it is impossible to replicate Rawls's original position completely, and thus it must remain a hypothetical thought experiment, it is possible to devise experimental conditions that approximate the original position.  Norman Frohlich, Joe Oppenheimer, and others have organized behavioral experiments in which people are put in conditions that approximate the procedures of the original condition.  Participants come together in small groups, and in choosing from a list of principles of justice for allocating resources in their group, they must reach unanimous agreement on their choice, without the participants knowing what their class position will be in that society.  They are then randomly assigned to high or low social positions, and they receive monetary payoffs based on the principle they have chosen.  Experiments of this sort have been conducted with university students in the United States, Canada, the Philippines, Japan, and communist Poland.

Remarkably, the outcome is uniform across all of these cultures.  Rawls's difference principle is almost never chosen.  By far the most common choice (in over three-fourths of the cases) is a floor constraint without a ceiling--that is, there is a minimum income guaranteed for the worst off, but there is no limit on the income that can be earned by the richest.  The next most common choice (in about 12% of the cases) is the principle of maximum income (no floor, no ceiling).  The third most common choice (in about 8% of the cases) is the principle of a range constraint--there could be economic inequality, but the gap between the richest and the poorest would be limited.  The difference principle--that no person's income can go up unless it increases the income of the people at the bottom--was chosen in only 1% of the cases, and they were all in communist Poland.

When participants are asked to explain their choices, they indicate that are trying to balance three distinct ethical claims--need, just deserts, and efficiency.  They think it's fair that those who are least well-off should have their minimal needs secured.  But they also think that those who earn higher incomes deserve this reward.  And they think that higher incomes for those who succeed is economically efficient in providing incentives for productivity that benefits everyone.

The most commonly chosen principle--floor constraint without a ceiling--looks a lot like what Friedrich von Hayek proposes in Part Three of The Constitution of Liberty: a largely free market economy combined with a welfare state that provides a minimal standard of security for all.

This seems to weaken Thomas Piketty's appeal to the Rawlsian difference principle as justifying confiscatory tax rates on high incomes and wealth for the sake of reducing inequality.

Remarkably, towards the end of his life, Rawls conceded what Frohlich and Oppenheimer had revealed in their experiments--that in circumstances of impartiality approximating the Rawlsian original condition, reasonable people would not all choose the difference principle but would rather choose the principle of a floor constraint without a ceiling.  In 1995, in his introduction to the paperback edition of Political Liberalism, Rawls admitted that while he still thought that "justice as fairness"--with its two principles of justice, including the difference principle--was the most reasonable conception of liberalism, there were other reasonable conceptions of liberal justice, including, for example, "one that substitutes for the difference principle, a principle to improve social well-being subject to a constraint guaranteeing for everyone a sufficient level of adequate all-purpose means" (xlvii).


Frohlich, Norman, Joe A. Oppenheimer, and Cheryl Eavey, "Laboratory Results on Rawls's Distributive Justice," British Journal of Political Science 7 (1987): 1-21.

Frohlich, Norman, and Joe A. Oppenheimer, Choosing Justice: An Experimental Approach to Ethical Theory (Berkeley: University of California Press, 1992).

Lissowski, Grzegorz, Tadeusz Tyszka, and Wlodzimierz Okrasa, "Principles of Distributive Justice Experiements in Poland and America," Journal of Conflict Resolution 35 (1991): 98-119.

Rawls, John, Political Liberalism, expanded edition (New York: Columbia University Press, 2005).

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