Voluntary Acts, Psychology Of

There is a deeply rooted and widely held moral intuition to the effect that a person is responsible only for what he does voluntarily. This intuition is the basis for doctrines of both criminal law and tort law. Although most forms of liability in criminal law or in tort rest on some form of culpability or fault (such as purpose, knowledge, recklessness, or negligence), strict liability crimes or torts require only a voluntary act or omission of a specified type.

In criminal law, the prosecution has traditionally been required to prove that the defendant performed an actus reus (voluntary conduct) with a certain mens rea (guilty state of mind), and that this voluntary conduct caused the proscribed harm to the victim or constituted the proscribed type of behavior. Courts hold individuals liable in tort for conduct that causes harm intentionally, negligently, or in strict liability. That [Page 1566]conduct may take the form of action or of the failure to act when the individual had the duty and ability to act.

Aristotle (384–322 BCE) was the first philosopher to analyze voluntariness and responsibility. He defined voluntary action largely by exclusion, by specifying the conditions under which one should morally excuse an actor's conduct on grounds of involuntariness. According to Aristotle, an agent is responsible for conduct unless (1) he “could not help it”—that is, he could not have stopped himself even if had he wanted to; or (2) he “did not know what he was doing” and his ignorance was nonculpable. Aristotle's analysis of two kinds of involuntariness has held up remarkably well through the ages.