Some authors have argued that the nature of one’s moral judgments are fixed foremost by their epistemic circumstances. Epistemic considerations constrain the moral judgments that persons make about their own actions and those of others. If decision-making proceeds from epistemic to other normative considerations, then a person’s judgments about moral behavior in some set of circumstances should vary with their knowledge and ignorance of these circumstances. In this study, we test this hypothesis. We conducted two experiments, both using MTurk to observe participants’ responses to trolley problems. In each experiment, degree of ignorance of consequences was manipulated. In the second experiment, we also compared the effect of ignorance upon moral judgment with that of personal force, a variable previously shown to influence moral judgment. Across the two experiments, we found broad support for the notion that what one knows determines their moral judgement. These findings provide empirical support for the armchair arguments that epistemic considerations are logically prior to normative considerations. They also suggest that previous research on the factors that influence moral judgment should be reviewed through the lens of the decision-makers’ knowledge and ignorance.