Inferring Consent without Communication

Some claim that consent requires common knowledge. For a doctor to obtain consent, a doctor must know that her patient has given her permission to perform surgery, and her patient must know the doctor knows that he has given this permission. Some claim that such common knowledge requires communication, and so consent requires communication: the patient must tell the doctor he consents for both to know consent took place, and for both to know the other knows consent took place. I first defend the claim that consent requires common knowledge, responding to recent objections. I then argue that, though consent requires common knowledge, it does not always require communication. It does not require communication when the agent obtaining consent can infer common knowledge based on non-behavioral facts about the world.