Calls for more broad-based, integrated, useful knowledge now abound in the world of global environmental change (GEC) science. They evidence many scientists’ desire to help humanity confront the momentous biophysical implications of its own actions. But they also reveal a limited conception of social science and virtually ignore the humanities. They thereby endorse a stunted conception of ‘human dimensions’ at a time when the challenges posed by GEC are increasing in magnitude, scale and scope. Here we make the case for a richer conception predicated on broader intellectual engagement. We then identify some of its practical preconditions. Interdisciplinary dialogue, we suggest, should engender plural representations of Earth’s present and future reflective of divergent human values and aspirations. In turn, this might insure publics and decision makers against overly narrow conceptions of what is possible and desirable as they consider the profound questions raised by GEC.