In ‘Justice and Nature’, Thomas Nagel claims that social institutions are not responsible for inequalities caused primarily by nature, as opposed to socially caused inequalities. I evaluate this claim. To do so, I distinguish causal responsibility from substantive responsibility. I argue that Nagel rightly identifies conditions in virtue of which social institutions are not substantively responsible for an inequality, but the causal responsibility of nature is irrelevant for that assessment. The natural/social distinction is, I hold, misleading, and I offer two (...) pragmatic reasons to stop using it. Besides, past criticisms to the natural/social distinction have questioned whether identifying the causal responsability of nature for an inequality is descriptively meaningful, epistemically possible, and morally relevant. My reconstruction of Nagel’s view avoids these criticisms, I explain, by depriving the causal responsibility of nature of any role to identify an inequality as naturally caused. Moreover, I show that my reconstruction of Nagel’s view, purged of the natural/social distinction, helps to justify the asymmetrical treatment of class-based inequalities and inequalities among people with different native endowments in the Rawlsian principle of fair equality of opportunity. (shrink)