In its most basic sense, assumption of risk means that the plaintiff, in advance, has given his express consent to relieve the defendant of an obligation of conduct toward him, and to take his chances of injury from a known risk arising from what the defendant is to do or leave undone. The situation is then the same as where the plaintiff consents to the infliction of what would otherwise be an intentional tort, except that the consent is to run the risk of unintended injury, to take a chance, rather than to accept the greater certainty of intended harm. The result is that the defendant is relieved of legal duty to the plaintiff; and being under no duty, he cannot be charged with negligence.