In this chapter, I develop an account of the ways in which the criminal law upholds fair terms of interaction. My emphasis is on the idea of interaction. As a result, my central focus will be on the two kinds of cases in which the rights of two people are at issue, namely, self-defense and consent. Where they are applicable, both self-defense and victim consent provide complete defenses to criminal charges. They are also the two areas in which reasonableness tests apply to mistakes. I will explain the underlying idea of reasonableness, and thus the role of those tests, in light of the ideas of fair terms of interaction I developed in my account of tort. Where the criminal law employs reasonableness tests, they are sometimes thought to rest on an evaluation of the plausibility of the accused's beliefs, given available evidence. The burden of this chapter is to show that reasonableness tests are deeper, indeed constitutive of the rights the criminal law protects. Here, as elsewhere, the reasonable person is the one who interacts with others on terms of reciprocity.

MISTAKES

Mistakes enter the criminal law in two distinct ways. Sometimes, mistake is an excuse, regardless of how stupid the mistake might be. If one person takes another's raincoat, genuinely mistaking it for his own, no matter how stupid his mistake, he commits no crime. Again, the person who kills another person by firing a gun she believes to be unloaded commits at most manslaughter, not murder.