PARIS — So who was Stephen Paddock? Was the Las Vegas assassin a "very, very sick individual", as described by Donald Trump? Or a jihadist combatant, recently converted, as ISIS maintains? Or both — or neither? For now, there is no clear response to these questions. But an analogous perplexity returns, again and again, as acts of violence proliferate around the world. In France, in Europe, in the United States, from knife attacks to truck massacres, from shootings to assaults, the same question continues to resurfaces: are we dealing with a "real" terrorist or a mentally ill person? A fanatic or someone unstable? I believe that while this question no doubt is legitimate, it is extremely limited. What is worse, instead, is that it risks making us blind to a more fundamental philosophical analysis that is sorely needed.

The practical scope of this question has to do with the police, first and foremost. The investigation is vastly different, for the police and for the specialized services, if an assailant is a psychopath caught up in some fit of delirium rather than a trained jihadist, acting on orders, as part of a network, controlled by an organization. Despite all this, the boundary between the two is not necessarily easy to trace, because multiple factors tend to blur together.

Psychiatric diagnoses can be limited, especially if made after the fact, without files from hospital monitoring, based solely on a posthumous bundle of clues and information. On its end, ISIS, at the height of a period of difficulty, can benefit from claiming "franchise" murders committed by unstable personalities, seizing the scenario offered by current events to do this. In the end, for various reasons, good and bad – that's another debate – the media and political powers can choose to remain wary, sometimes excessively so.

Isn't the fanatic's judgment also altered?

The eye of the philosopher is not burdened with these precautions. What interests us, first of all, are the definitions of what we're talking about, the concepts involved. Yet, on this scale, between the fanatic and the unstable person, it is very difficult to find a definition that is truly clear and distinct. The terrorist is a person with a sound mind, ‘radicalized," but not truly insane. This person is fully resolved to kill strangers, to sacrifice their own life in a massacre, but this is an effect of jihadist propaganda, of ‘radicalization," not of insanity. In contrast, the ‘unstable person" is affected by psychosis, altering their judgment, opening them up to hallucinations, to imaginary persecution and to compulsive actions.

One doesn't need to be a great scholar to notice that there is something unsound about this approach. Isn't the fanatic's judgment also altered? Isn't their vision of the world hallucinated, phantasmagorical, delirious? To fully adhere to that propaganda, to be able to launch oneself into a suicide attack, mustn't the terrorist be mentally unstable? Or is he damaged, made crazy, mentally disrupted by the barbaric training that the jihadists subjected him to?

To understand the extent to which we make mistaken categorizations while striving with all our might to set the figure of fighter against that of the sick person, it suffices to reread Voltaire. What does he call "fanaticism"? "A dark, cruel religious madness," "a sickness of the mind." For him, there was no distinction between fanaticism and pathology. "When fanaticism has corrupted the brain, the sickness is almost incurable." How does this work? "It is the effect of a false conscience that makes religion a slave to the caprices of the imagination and the disruptions of the passions," wrote the French philosopher in the entry "fanaticism" in his 1764 "Philosophical Dictionary."

Though the vocabulary has aged, the ideas behind it stand up over time. Fanaticism is a pathology of religious faith. The only definitive criterion that distinguishes a "normal" believer from a fanatic – who appears to be unstable by definition – is the imposition of the truth through violence. What they consider to be true, the fanatic imposes on all others, on society, on the world, on history – by any means, including the most inhumane. They find themselves justified, through their own eyes, by the single truth they support. Fanaticism is an absolute rejection of pluralism. In this sense, it is always madness.