“Actus non facit reum nisi mens sit rea”. The Concept of Guilt in the Age of Cognitive Science

According to a famous brocardo (i.e., an ancient legal maxim), “Actus non facit reum nisi mens sit rea”, culpability exists only when the author of a crime has committed it with a criminal intention. Nowadays it is commonly held that, barring some minor exceptions, this maxim states a necessary condition of culpability. From a philosophical point of view, however, two problems must still be discussed in regard to it. First, because of the so-called “deviant causal chain”, it can happen that a mens rea causes an actus reus, without producing culpability; however, no satisfactory criteria for distinguishing such cases from the ordinary ones has ever been individuated. Second, a growing number of scientists and philosophers suggest that our conscious mental states rarely (if ever) determine our decisions and actions. If this is correct, a mens rea causes an actus reus rarely (if ever), and, consequently, culpability should be seen as a rare condition – if it is ever real. After analyzing these issues, my conclusions will be that, even if it may be true that the cases in which we consciously control what we decide and do are more limited than we would like to think, they still do exist. The ancient brocardo, then, still holds its validity.