The unique characteristics of ideas make material progress possible. But that’s not all: Ideas matter not just for what humans have, but also for how they are. During the Pleistocene Epoch, human nature evolved in a Malthusian world of objects. We developed an ugly tendency to split humanity into “us” and “them.” A world that also includes ideas justifies a new mindset that treats all humans with the dignity and respect that we offer to “us.” It is a world in which we may derive net material benefits from the presence of others.