From Self‐Interest Motives to Justice Motives: The Challenges of Some Experimental Results

. This article begins by presenting experimental evidence that remains unexplained by standard and utility‐extended economic models: experimental subjects tend to honor their promises even on occasions when an assessment of consequences asks them to defect; subjects voluntarily contribute to collective goods, and this contribution is highly conditional on others contributing as well; subjects evaluate and value the intentions behind actions as well as the consequences of actions. Arguments are sought for in moral philosophy that would more plainly explain the collected experimental evidence and that would help economists revise their explanatory frames. The hypothesis advanced is that the observed behavior may be interpreted as resulting from the moral strength of indignation and justice norms.