"Even a dog distinguishes between being stumbled over and being kicked." (1)
The thesis of this essay is simple: As long as we maintain the current conception of ourselves as intentional and potentially rational creatures, as people and not simply as machines, the mens rea requirement in criminal law is both inevitable and desirable. I begin with the challenge to personhood, action and responsibility that recent work in psychology and neuroscience allegedly present. Then I turn to some dangerous distractions that are often confused with the questions of personhood, action and responsibility. The next section explains why the genuine challenge from neuroscience can be met. Finally, I turn to the positive case for mens rea. I do not argue for any particular categorization or hierarchy of mens rea terms. (2) Instead, I argue more generally that mens rea, which is understood to be the mental state element that is part of the definition of most criminal offenses, (3) is crucial to culpability and central to our value as moral beings.
I. THE CHALLENGE TO PERSONHOOD, ACTION, AND RESPONSIBILITY
As I type the words of this paper, I have an experience that virtually every neurologically intact human being takes for granted: the subjective experience of first person agency, the experience of mental causation, that my bodily movements and thoughts are caused, roughly speaking, by my intentions. (4) To the best of our knowledge, only human beings have a fully developed capacity to act for reasons. This description sounds like Cartesian dualism--the notion that we have an immaterial mind or soul that is somehow in causal relation with our physical body and that causes it to move as the mind directs. But I fully accept that we inhabit a thoroughly material universe in which all phenomena are caused by physical laws. In particular, human action and consciousness are produced by the brain, a material organ that works according to biophysical laws. At present, however, we do not have a clue about how the brain enables the mind, or about how action and consciousness are possible. (5) Understanding how the brain enables the mind would revolutionize our understanding of biological processes and the nature of personhood, (6) but such understanding may not be possible. (7)
Although action and consciousness are scientific and conceptual mysteries, (8) they are at the heart of both common sense, "folk psychology," and the conception of the person inherent in judgments about responsibility and culpability. The capacity for intentional movement and thoughts-the capacity for agency--is a central aspect of personhood and is integral to what it means to be a responsible person. We act because we intend. Responsibility judgments depend on the mental states that produce and accompany our bodily movements. This is how we think about ourselves, and this is the concept of the person that morality and law both reflect. Law and morality as action-guiding normative systems of rules are useless, and perhaps incoherent, unless one accepts this view of personhood.
Virtually everything for which we deserve to be praised, blamed, rewarded or punished is the product of mental causation and, in principle, responsive to reason. Machines may cause harm, but they cannot do wrong, and they cannot violate expectations about how we ought to live together. Only people can violate expectations of what they owe each other, and only people can do wrong. Machines do not deserve praise, blame, reward or punishment. Machines do not deserve concern and respect simply because they exist. These concepts apply only to potentially acting, intentional agents.
Suppose, however, that our conscious or potentially conscious intentions are not genuinely causal or seldom are so. To use the title of a recent book by an eminent psychologist, suppose that our "conscious will" is just an illusion. (9) Ordinary …