Stephen Mathis on 'Distinguishing Violent Extremism from Criminal Insanity' for the Extreme Beliefs and Responsibility workshop at Vrije Universiteit Amsterdam.

Stephen Mathis is a postdoctoral researcher at the University of Bergen, Norway. He received his PhD from the University of Kansas and taught for many years at Wheaton College in Norton, Massachusetts before moving to Norway. His previous work addressed action theoretical questions in the criminal law, but now he is working with researchers in law, psychiatry, and philosophy to explore the different disciplinary dimensions of the insanity defense. Through this grant-funded project, which is called DIMENSIONS, he is researching the interaction between mental disorder, action, and criminal responsibility, with a particular interest in practical reason, extremism, and volitional impairments.

Abstract
While psychiatry has offered a tentative explanation of the difference between delusional beliefs and extreme overvalued beliefs (EOBs), researchers have admitted that distinguishing between the two in practice is quite difficult. This has also become clear in a number of high profile court cases where the issue at stake is to determine whether the defendant, whose motives have been extremist, [SR1] [SR2] should be held responsible for his actions. The question of whether the motives of the defendant were delusional or “just” overvalued has come to the forefront.
The issue here is however not just the psychiatric diagnoses, since the insanity doctrine in criminal law and determinations of responsibility in general are normative endeavors. That is not to say that they cannot be informed by empirical data, but just that the core of the relevant judgment is not a purely scientific one. The unreasonableness of extremist views, delusional or not, also plays a role in the decision about whether a defendant should be subject to scrutiny under the criminal law.
Toward the end of drawing a helpful normative distinction between violent extremism and criminal insanity, we appropriate and modify John Rawls’ distinction between the rational and the reasonable. We adopt the general idea of reasonableness as being willing to cooperate fairly with others to live together in society. However, for the sake of this paper, we suggest understanding rationality more generally than Rawls does: the idea of rationality we want to employ is characterized by the ability to provide and evaluate reasons and to plan and act in accordance with them. Armed with that distinction, we argue that violent extremists are not irrational, but they are characteristically unreasonable; and the criminally insane may be unreasonable, but the characteristic feature of their mental incapacity is that they are not rational at the time they act.
Mapping (albeit roughly) the distinction between violent extremism and criminal insanity onto this version of the (un)rational and the (un)reasonable in this way opens the door to normative explanations that empirical data cannot provide. It can also inform psychiatry’s distinction between delusions and EOBs. Most importantly, however, this mapping makes clearer that it is the deeply unreasonable character of the beliefs that violent extremists espouse and act upon that explaining why those beliefs and those actions are so deeply objectionable.