I understand humanism to be the meta-ethical view that there exist discoverable (nonmoral) truths about the human condition, that is, about what it means to be human. We might think that as long as I believe I am realizing my unique human potential, I cannot be reasonably contradicted. Yet when we consider systemic oppression, this is unlikely. Systemic oppression makes dehumanizing conditions and treatment seem reasonable. In this paper, I consider the nature of understanding—drawing in particular upon recent defenses of realism in the philosophy of science—and argue that humanism makes sense if we recognize more thoroughly the role of cause and effect in practical deliberation. By this I mean the cause-and-effect relation between mind and body and between minds, bodies, and the world. Three philosophical sources—Marxism, Buddhism and Christianity—show what this might mean, as I indicate in the second half of the paper.