Orthodox contractualists and rule consequentialists think that, for any action, the consequences of everyone performing that action determine whether that action is permissible. For them, “what if everyone did that?” is the fundamental moral question. By making “what if everyone did that?” the fundamental question of good moral reasoning, these moral theories can easily justify prohibitions on free-riding. But it also makes them face the ideal world problem. I argue that it was a mistake for moral theorists to generalize from an objection appropriate to cases of free-riding to all of morality. In short, we should understand the question “what if everyone did that?” to give expression to one, and only one, kind of objection to one’s action—namely, that, by performing that action, one would be making an exception of oneself. If we limit the scope of “what if everyone did that?” in this way, we can justify prohibitions on free-riding while avoiding the ideal world problem.

This essay provides a comprehensive and critical introduction to ideology. It traces the origins and development of various conceptions of ideology, articulating both what they have in common and their differences. Among the distinctions that we develop are the contrasts between pejorative and nonpejorative conceptions, functionalist and causal conceptions, and conceptions that limit ideologies to supporting existing oppressive orders and those that allow for ideologies that challenge such orders. We also explain the role that ideologies can play in either preventing or facilitating social movements to overturn or improve existing institutions. The concluding section of this essay provides a list of important topics for future research on ideology and emphasizes that, in each case, an interdisciplinary approach is needed to understand them fully.

Although diversity has often been proposed to improve group performance, its impact on group cooperation has largely been overlooked. This article uses a theoretical approach to examine the effects of diversity on group tasks in the context of the free-rider problem. We identified 3 kinds of diversity that have been commonly reported to improve a group’s performance: (1) ability, (2) cognitive style, and (3) information sources. Each type of diversity was formalized within an evolutionary simulation based on a foraging metaphor. The simulations were run under different environmental assumptions, covering complexity, costs for cooperation, cue redundancy, and cue compensatory level. Our results indicate that diversity in cognitive style and information sources generally increase cooperation. Both diversity factors also improve group members’ average outcome in non-compensatory environments. However, the outcome results are mixed in compensatory environments. We did not find robust and reliable effects of diversity in ability. Our study provides the first approach to modeling isolated diversity effects on group decision-making in the face of the free-rider problem. It may serve as a theoretical framework for future studies.