In recent years the EU has experienced a bewildering wave of terrorist attacks from groups and individuals.
According to a number of studies, terrorism in Europe has killed 11,288 people in 18,811 attacks since 1970.
Extremist ideologies, perpetrated by actors often sponsored from abroad, have proven to be a decisive factor in promoting radicalisation within the EU and a driving force behind terrorist attacks.
Furthermore, the growing influence of cyberspace facilitates rapid radicalisation processes and produces unpredictable and random threats.
Following the March 2016 Brussels attacks, the list of European cities affected by terrorism continues to grow. According to Europol, the primary preoccupation reported by EU Member States in the last three years continues to be jihadist terrorism, though extreme left and extreme right are also of concern.
And what of the ideologies that inspire terrorism?
With regard to Islamism, the primary concern is that many of the 5000 foreign fighters originating from the EU are likely to return. In addition, those who have been prevented from departing also pose a threat and may redirect their focus against Europe. In both cases, the ideological indoctrination to which they have been exposed represents a serious cause for concern, as Europol confirms.
"It is crucial that our focus needs to be not only on the prevention of terrorism, but also on the prevention of radicalisation that can lead to terrorism"
Regarding left-wing extremism, according to Europol, in 2016 Europe saw the highest incidence of attacks. By contrast, the number of arrests of left-wing offenders was half the 2015 figure. While it is difficult to identify independent left-wing extremists travelling around Europe to participate in violence, a form of positive bias persists among policy-makers, insofar as extreme leftists would fight for "noble causes" - challenging capitalism, imperialism, nationalism and fascism.
The same binary worldview characterises extreme-right ideologies. While the majority of EU member states consider the risk of violent right-wing extremism to be low, this does not mean there is no danger. First, the threat may escalate: German statistics for 2016 reveal almost 50 per cent of right-wing extremists considered violence an option. Second, the xenophobic, divisive and anti-democratic ideology they promote is already a threat, per se.
Indeed, two main points are worth highlighting with regard to terrorism. First, violence does not occur at random - there’s usually a specific ideology behind it. Second, the three main ideologies inspiring global terrorist attacks all have commonalities: glorification of an irrational objective - a utopia; a Manichean dualist division of society; Machiavellianism (the end justifies the means); and determinism (the utopia will inevitably come into being).
Violence is just one among a number of possible tools to be used to achieve utopia. As the recent Belgian Parliament's inquiry on the Brussels attacks highlights, extremists pursue non-democratic goals, but not always through non-democratic means: another tactic is the exploitation of democracy to attain power and ultimately vanquish non-believers.
This is why it is crucial that our focus needs to be not only on the prevention of terrorism, but also on the prevention of radicalisation that can lead to terrorism.
Requiring non-violent radical groups to reject violence alone is insufficient. We cannot have neo-Nazi, Islamist or Stalinist groups as part of national or European counter-extremist strategies.
If governments continue to include non-violent radical groups in prevention initiatives, we not only risk alienating a generation of young Europeans: we threaten the very basis of our liberal-democratic value system, the raison d'être of the EU's existence.