Last month, CNN released video footage of Brahim Abdeslam and his younger brother Salah dancing in a nightclub alongside a blonde woman, with whom Brahim, the report claimed, was flirting. “This was life before Isis,” the voiceover to the report says. “It’s February 8, 2015. Just months later, Brahim would blow himself up at a Paris café; and Salah becomes Europe’s most wanted man.”

But was it life before Isis? The automatic assumption in the report is that drinking and flirting are indicative of a secular and thoroughly “unIslamised” state of mind — and that wannabe jihadis don’t jive or flirt. The report also assumes that something intense and convulsive happened to the Abdeslam brothers in the intervening period between February 8 and November 13 of last year, although it sheds no light on what that was. Among scholars, “radicalisation” is commonly understood as a gradual process in which people adopt ever more extreme postures and beliefs. It is widely thought that this process begins with a dramatic event or personal crisis, paving the way for a “cognitive opening” — a receptivity to alternative views and perspectives — and a period of religious seeking, often mediated by an extremist mentor and a wider social network.

“Radicalisation,” viewed from this perspective, is a process of self-transformation, where the transformed person comes to view themselves and the outside world in a fundamentally different light. And although scholars disagree over exactly how and where this occurs, there is a broad consensus that radical self-change lies at the heart of the process and that terrorism, although not an automatic outcome of radicalisation, is inexplicable outside of it.

The assumption is that while not all radicals become terrorists, all terrorists are radicals.

The Abdeslam brothers, with their sudden escalation from dancing in nightclubs to killing in them over the course of a few months, seem to challenge this picture.

They also raise a deeper and more troubling question for those seeking to understand the genesis of terrorist acts: what if they were not “radicalised” and underwent no dramatic metamorphosis at all? What if their violence had only the most tenuous connection to what they believed, whatever that was?

What if the story of how they came to be involved in terrorism had no real coherent narrative arc? What if the script of terrorism doesn’t always feature the drama of radicalisation?

According to one of the two friends who filmed the nightclub footage, the Abdeslam brothers “were nice people ... I suppose you could say they lived life to the full”.

The other friend, going by the name “Karim”, adds: “I saw Salah joke, smoke, drink, and play cards ... If anything, he liked women. He was something of a ladies’ man, and I heard he had a girlfriend at one point.”

The CNN report continues: “At the time, the friends said they had no idea that the two had embarked upon their journey towards radicalism ... ‘They must have been changing bit by bit.’”

Or not. According to a Sunday Times report, Salah Abdeslam was seen in a gay bar as recently as a month before the Paris attacks.

The report also quotes Karim, an apparent close friend of the brothers: “Brahim and Salah spent most of their days smoking hashish and playing on PlayStation in the bar ... There was nothing to suggest they were radicalised.”

Referring to the secular lifestyles of the November 2015 Paris attackers, Islam expert Mathieu Guidère suggests that this behaviour “may have been an example of taqiya, or calculated pretence, in which the warrior preparing for ‘martyrdom’ melts in with the enemy, adopting his way of life, to avoid detection”. Or it may have been no such thing, given that the Abdeslam brothers, unlike the 9/11 attackers who shaved their beards and visited strip clubs in the months before their mission, were not operating in enemy territory but in indifferent and supposedly jihadi-friendly Molenbeek.

Another possibility is that the Abdeslam brothers were in the process of becoming radical jihadis and that their secular habits were a hangover from the previous lifestyles that they were trying to walk away from. Another is that they were, in fact, radicalised but living in a state of cognitive dissonance, drinking and dancing the one minute, and railing against the ways of the kafir the next, much like the righteous men in Laud Humphreys’s Tearoom Trade, who, when not publicly bemoaning the decline of family values, were out cruising for gay sex in restrooms.

But perhaps the more realistic — and in some ways more unsettling — scenario is that the Abdeslam brothers drifted in and out of jihadi activism and that this owed more to who they knew and how they lived than anything they believed.

More than half-a-century ago, the criminologist David Matza described, in a now classic text, how juvenile delinquents drift in and out of delinquency. They are able to do this, Matza argued, because the delinquent subculture, in its embrace of excitement, its disdain for work, and its celebration of violent machismo, is actually an extension rather than a rejection of conventional society.

There is no ideological conversion to an alternative deviant worldview, Matza posited — just a temporary crossing over to a subterranean world that embodied, in grotesque caricature, the codes of mainstream society.

Despite its seeming exotic otherness, and for all its theological quiddities, the world of the Islamic State is not wholly disconnected from that of our own. Its ideals of heroic self-sacrifice, adventure, violence and machismo are mirrored, albeit in a secularised and far more muted form, in our own culture; they find less constrained expression, for example, in our movies. In other words, the breach between those who join the Islamic State and “us” is not as deep as we would like to think. It is even narrower in the case of Molenbeek in Brussels, where a hybrid subculture of crime, violence and jihadi activism has taken root. The Washington Post’s Anthony Faiola and Souad Mekhennet describe members of this subculture as “part terrorist, part gangster”: liminal badasses who exist between two overlapping worlds, for whom, as terrorism expert Rik Coolsaet documents in a recent study of Belgian foreign fighters in Syria and Iraq, “joining [the Islamic State] is merely a shift to another form of deviant behaviour, next to membership of street gangs, rioting, drug trafficking and juvenile delinquency.”

Whether terrorists such as the Abdeslam brothers have been “radicalised” in the traditional sense is more than a matter of academic debate. Government programmes aimed at countering violent extremism have embraced the transformational view of radicalisation: implicit in their language and rhetoric is the idea that terrorism is the end stage of a process in which people come to adopt an extremist worldview that justifies violence. CVE tries to map out this process, identifying signs of radicalisation, which include changes in personal appearance and the “overt expression of hyper-religiosity”, so as to intervene to obstruct its development. Yet cases such as the Abdeslam brothers’ highlight the possibility that, when it comes to CVE, we still have very little idea of what actually constitutes best practices. As terrorism scholar John Horgan observed, “there is evidence that not all those who engage in violent behaviour necessarily need to possess radical beliefs.” He elaborates: “A lingering question in terrorism studies is whether violent beliefs precede violent action, and it seems to be the case that while they often do, it is not always the case.”

In the coming weeks and months, the world’s media will continue to wonder how the “well-liked” and “ever so normal” Abdeslam brothers became ardent jihadis at war with the West, mining their pasts and our own failures and wrongdoings to explain what “drove” this transformation.

Yet it is possible that no such transformation occurred.

This is not a good story because it contains no dramatic epiphanies or conversions. But it may turn out to be true.

• Simon Cottee is a senior lecturer in criminology at Kent University in England and the author of The Apostates: When Muslims Leave Islam