Suppose we believe that ignorance of wrongdoing should often absolve wrongdoers from blame, criminal liability, and punishment. If so, how should this normative belief be reflected in the structure of criminal law? One of many possible solutions is to include ignorance of wrongdoing (when it is exculpatory) within the scope of mens rea. In other words, we might adopt the following thesis: defendants who are unaware their conduct is wrongful do not commit the mens rea of the offense that (otherwise) proscribes their conduct. In this paper I explore what can be said for and against this thesis. I expect most theorists will resist it, and I readily admit that it is likely to have implications that should give us pause. But I believe this thesis also has considerable advantages that are easy to overlook. The particular advantage I will emphasize in what follows draws from dissatisfaction with the most recent Supreme Court decision on the insanity defense. Reasonable minds will differ about whether the advantages of this thesis outweigh its disadvantages. Overall, however, I tentatively conclude that it has a great deal of merit and should probably be adopted.