A historically responsible agent is willing to be somehow in practical solidarity with all other actors with whom action is shared over time. The responsible idea of a most-inclusive history encompasses future occurrence together with all that has happened already. Despite our lack of control over future developments, we assess possible future ages as bright (if action opportunities are generally greater) or dark (if lesser) and position ourselves as contributors to multigenerational endeavors (such as Burke’s “all science” and “all art”) that we hope will be long-term successes in themselves and part of a larger historical optimality. Informed by the evolutionary sciences, a plausible modern envisioning of the future must include evolutionary innovations and surprises on a very long time scale. The historically responsible agent will therefore take seriously efforts like Olaf Stapledon’s Last and First Men to imagine the new powers and goals of our distantly posthuman future sharers in history.