Conscience can err. Yet erroneous conscience still seems binding in that it is likely to be morally wrong to ignore the call of conscience. Meanwhile, it seems equally wrong to act according to such a wrong judgment of conscience. The moral dilemma of erroneous conscience poses a challenge to any coherent theory of conscience. In light of this, I will examine Aquinas’s reflections on the psychological mechanism of erroneous conscience and reconstruct a sophisticated explanation of the obligatory force of erroneous (...) conscience, in which the conscientious integrity of the agent is intimately integrated with the sovereignty of divine law. Next, I will appeal to Aquinas’s distinction between the judgment of conscience (iudicium consentiae) and that of free decision (iudicium liberi arbitrii) to show that the judgments pertaining to conscience are purely cognitive rather than affective. This analysis will also help specify in what sense we can tolerate conscience’s wrong judgments. (shrink)