Kalashnikovs trained on free speech, police protection for Jewish schools and 10,000 troops out on “sensitive” streets in Britain’s nearest neighbour. The last few days in Paris stir searching questions about the nature of European society, the values it holds dear, and the right way to protect them. One might hope for answers reflecting fresh thinking, but the emerging response of SW1 is drearily familiar – mass surveillance on the assumption that “the gentleman from Whitehall knows best”.

When public health or industrial prosperity is the issue, the libertarian right reliably challenges the sloppy idea that fresh state powers constitute an automatic solution. After Paris, however, Conservative voices, including the prime minister and the supposed intelligence and security watchdog, Sir Malcolm Rifkind, have been queuing up to echo MI5’s demand to strengthen the arm of the authorities against the individual. The snooper’s charter is a bill which refuses to die. The campaign to force communications companies to keep and provide access to call and internet records began when Labour was in power and was revived in modified form under the coalition. Nick Clegg claimed to have killed the scheme in 2013, but within weeks elements crept back into contention via a bland passage in the Queen’s Speech. Then the world learnt – courtesy of Edward Snowden – that the desperation for this legislation reflected an urge to cover backs for things that were already being done. Exposing the motive did not dull the impulse. In November, Robert Hannigan took up the reins at GCHQ and returned to the theme. Then, last week, Andrew Parker of MI5 made the same point in the wake of Paris.

Next to such horrors, it is easy to belittle any unease about prying – easy but mistaken. The writer John Lanchester concedes that democracies will always need spies, but reading the Snowden documents persuaded him that piecing together habits of thought from internet searches takes things far beyond conventional spying: “Google doesn’t just know you’re gay before you tell your mum; it knows you’re gay before you do. And now GCHQ does too.” Eight centuries on from Magna Carta, the potential to follow every last electronic trace rewrites the contract between citizen and state. Yet in Paris, as in so many cases before, mass surveillance turns out to be beside the point.

The Paris gunmen had been on watchlists for years. Building up extra intelligence on all 66 million residents of France would not have helped; keeping an unflinching eye on the few thousands who provoke serious fears might have done. If the question were resources, the spies would deserve a fair hearing. But they seem more interested in the power to add hay to the stack, a perverse way to hunt the needle. For all the claims made for untargeted sifting, the sole “plot” that the US authorities can hold up as having been disrupted by it is a taxi driver’s payment of a few thousand dollars to al-Shabbab. Terrorists, from 9/11 to the Woolwich jihadists and the neo-Nazi Anders Breivik have almost always come to the authorities’ attention before murdering. Society can’t afford too many scruples about the privacy of those who provoke such suspicions.

But snooping on everybody shreds the implicit consent on which all effective government activity – including legitimately secret activity – must rest. Whitehall is currently digging in against special protection for the call records of lawyers and journalists, betraying contempt for legal privilege and anonymous sources, a refusal to strike sensible balances that can only alienate support. Meanwhile, the spies air anxiety about the tech giants strengthening encryption to keep customers’ secrets safe, as if this reflected some anarchic west coast philosophy, as opposed to a hard-headed recognition that you don’t stay in business by disregarding clients’ anxieties. Sustainable spying is going to need the co-operation of these firms and the citizens who use them.

The agencies are understandably reluctant to get into operational detail, but it was reasonable to expect them to engage over the principles they applied prior to Paris. It remains reasonable still. Their work may be secret, but it is carried out on behalf of a public, which surely has a right to know about how the public interest is defined.