Among the most chilling consequences of the latest outrage in France is the strong sense that further atrocities are inevitable and the feeling of sheer helplessness which is growing among ordinary people.
Police patrols can always be increased, and huge searches carried out for guns and explosives, but it is almost impossible to prevent a lone suicide attacker from getting behind the wheel of a hired truck and ploughing into a group of innocent bystanders.
The level of fanaticism involved in the ISIS movement is very difficult for non-Muslims to comprehend, and suggestions are sometimes made that there must be a way to engage in at least tentative negotiations with its leaders.
However, they have regularly made it clear that they are determined not just to conquer sections of north Africa and the Middle East but to entirely overthrow western civilisation and establish a worldwide Islamic regime known as a caliphate.
ISIS representatives have let it be known that they are not interested in talking to their perceived enemies, and, in an authenticated statement sent out in 2014 from one of their main strongholds, Mosul in Iraq, summed up their message by saying that all those who did not accept their interpretation of the Koran would have to be killed.
The reasons for the development of ISIS over the last decade need to be studied closely but the priority must be to prevent its influence spreading beyond its power base in north Africa and to protect vulnerable people in a range of European countries from its sinister plans.
While France deserves enormous credit for the comprehensive structures which ensured the safety of football supporters attending the month-long European Championships, it is plain that extremists linked to ISIS were happy to wait until the tournament ended before launching another deadly onslaught.
The carnage in Nice, where well over 80 men, women and children were killed when a 31-year-old French-Tunisian drove a heavy lorry into crowds of Bastille Day tourists along a popular seafront on Thursday night, followed a series of similarly appalling events across the country over the last 18 months, resulting in an overall death toll which is approaching 250.
We must all, in France and elsewhere, accept and fully cooperate with intensive security measures in potential target areas – which could be almost anywhere - and report any form of suspicious behaviour to the authorities without delay.
If ISIS believes that it can terrify the wider population into withdrawing from normal life, and bringing our society to a virtual standstill, it will almost certainly intensify its twisted and random murder campaign.
The best response, after praying for the victims of Nice, is to go about our usual activities, take all reasonable precautions and relentlessly defend our democratic principles in the face of evil.
