The Mysterious Case of the Reasonable Person

Who is the ‘reasonable person’, that ‘excellent but odious character’1 who seems to inhabit every nook and cranny of the common law? Until I read Arthur Ripstein’s book Equality, Responsibility and the Law, I thought I knew the answer. I generally understood the word ‘reasonable’, in legal contexts, to mean no more and no less than ‘justified’. A reasonable action is a justified action, a reasonable belief is a justified belief, a reasonable fear is a justified fear, a reasonable measure of care is a justified measure of care, etc. By the same token, the common law’s reasonable person (I fondly thought) is none other than a justified person, i.e. a person who is justified in all those aspects of her life that properly call for justification. She is justified in her actions, her beliefs, her fears, the measure of care she takes, and so on. Thus, to say that one’s actions or beliefs or emotions or attitudes etc. were those of the reasonable person is merely to say, in a typically roundabout lawyer’s way, that one’s actions or beliefs or emotions or attitudes etc. were justified ones. It may be thought that at least some of the law’s uses of its reasonableness standard plainly defy this interpretation, so that it should not have taken a philosophical virtuoso like Ripstein to alert me to its deficiencies. What about the familiar cases, mentioned in even the most pedestrian of criminal-law