Up to a point, the US is to guns as the Netherlands is to bicycles. Both bits of kit are widely owned, used and even venerated in their respective lands. Their users can mobilise powerful lobbies. On Saturday on the Haarlemmerstraat I saw an irate motorist get out of his vehicle to bawl at a cyclist. He was quickly surrounded by passers-by and forced back into his car. It was a more satisfactory outcome than some disputes between gun users. But then – and here’s where the analogy begins to give out – bikes aren’t generally designed to kill people.

‘Terrorism’ and ‘tragedy’ thrive in different semantic fields. After the murders in San Bernardino last week the media were at first stumped about whether to call it ‘terror’ or just another ‘tragic’ gun massacre. Fortunately, it’s turned out to be terrorism, and IS-inspired at that. Unislamic shootings, by contrast, are as American as apple pie. Gun murders in the US yield an annual harvest of about four 9/11s (that’s without accidents and suicides). The victims of mass shootings tragically find themselves in the crosshairs of a nutter with a gun – though the NRA and other lobbyists point out that insofar as the victims aren’t themselves armed, they’ve only themselves to blame.

There remains a nagging doubt that terrorism and tragedy bear a passing likeness – for instance, from the standpoint of the victims. But as James Coney from the FBI said about San Bernardino, things ‘pushed us off the cliff’ into diagnosing terrorism when the killers turned out to be ‘ideologically’ motivated. The cliff separating the high from the low ground proves, however, to be something of a molehill. Quite a lot of down-home gun slaughter is avowedly ideological. Jared Loughner, who took out six people in a failed assassination attempt on congresswoman Gabrielle Gifford in 2011, did so in his crusade against ‘federalist laws’. The Sandy Hook mass murderer Adam Lanza averred that ‘an AK-47 and enough ammunition could do more good than a thousand “teachers”, if one is truly interested in reforming the system.’

Such thoughts are not confined to a few psychotics. Others agree, often in mainstream forums. In the Washington Times a couple of years ago, the Fox News 'senior judicial analyst' Andrew Napolitano pointed out that as ‘we have been created in the image and likeness of God the Father, we are perfectly free just as He is’, a fact he adduced to show that ‘the Second Amendment’s protection of the right to keep and bear arms is not that it protects the right to shoot deer. It protects the right to shoot tyrants.’ It would seem that the Father bestows his blessing on any two-bit Timothy McVeigh with an outsize grudge over his tax bill and ordnance to match. Only the Founding Fathers’ enshrining of their right to carry 200-rounds-per-minute machine-guns – Napolitano concludes, echoing the views of the Supreme Court justice Antonin Scalia – is protecting everyone from ‘the mania and terror of a few’. Loughner, who acted on his conviction that the government was ‘fucking us over’, emerges as an all-American zero, a latter-day king of the wild frontier.

Meanwhile in the UK, a knife-wielder who reportedly said 'This is for Syria' while stabbing his victims in Leytonstone Tube station managed to set off a major media splash. Presumably from now on any attention-seeker who mentions the latest crusade while in flagrante, from carrying out a mugging to urinating in a public place, can expect similar airtime, with a suitably draconian securitising response.

Obviously there’s good and bad ideology, but sifting the one from the other can prove awkward. Loughton’s bid to kill Gifford was reportedly triggered by her failure to answer a question he had put to her in a public meeting: ‘What is government if words have no meaning?’ Their terror is our God-given freedom. San Bernardino may well not be the last ‘home-grown’ IS-inspired killing in the American homeland. Policy-makers will have to square an awkward triangle, comprising the following propositions:

1. Acts of terrorism, by common consent, need to be prevented ‘by all necessary means';
2. Weapons of mass killing, in the form of automatic weapons, are easily and legally available;
3. US-based IS sympathisers minded to perform acts like those in 1 have their job made much easier by the truth of 2.