Actus non facit reum, nisi mens sit rea. [The act is not criminal unless
the intent is criminal.]

--Legal maxim

Criminal statutes define conduct that falls below prescribed legal and moral
standards and thereby causes identifiable social harm. Not every instance of
unlawful conduct is punished, however, and not every social harm is re-
dressed. Thus, before beginning a discussion of specific criminal statutes, it
is necessary to explore some fundamental concepts that are critical to an un-
derstanding of the structure and application of the criminal law. This chap-
ter will focus on four criminal law concepts--the voluntary act, the mental
state, causation and social harm--that provide the foundation for most
criminal statutes and assist society in selecting those individuals who are
morally blameworthy and deserving of punishment.

To secure a conviction under a criminal statute, one element the govern-
ment must prove is that the defendant performed a voluntary act that re-
sulted in a social harm. The act must be voluntary because moral
blameworthiness can be more accurately assessed when there is some de-
gree of certainty that defendants have acted according to their own free will.
Furthermore, if one of the goals of punishment is deterring unlawful con-

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