British author/journalist Howard Jacobson is not impressed with The Mighty Greenwald.

So how fare our investigations into what makes someone want to kill cartoonists? (I’m assuming we know why they want to kill Jews.) Maybe, before pondering the education of a jihadist, we should ask a prior question: what makes a fanatic?

We were given some insight into this on Newsnight earlier this week when Evan Davis, growing nicely into his job, interviewed the lawyer, journalist and associate of Edward Snowden, Glenn Greenwald - a man strikingly deficient in the musculature necessary to essay a smile. The subject was surveillance and David Cameron’s call for more of it. There are, I accept, differing views on this. I, for example, am for having every member of the human family watched day and night by every possible means because the human family is currently dysfunctional and can’t be trusted. But I understand why others don’t think as I do. This puts me in a different category of person from Greenwald, who allows no beliefs that conflict with his and attributes those that do to a cowardly subservience to authority.

Leading Greenwald with expert gentleness into the gated hell that is his mind, Davis put the case for differing viewpoints. Nothing could have been more instructive than Greenwald’s dead expression - his mouth fixed in the rigor mortis of absolute conviction, his eyes unanimated by the pleasure of conversation or the excitement of controversy. Doubt honours a man, but this was the face of someone whom no ghost of a second thought dares visit. No consciousness of absurdity either. As for the humanity whose civil rights he champions with such icy rigidity, for that he had nothing but contempt. We are merely, if we don’t think what he thinks, the playthings of the powerful. This is the terrifying paradox of zealotry: no one hates humanity more than those who believe they know what’s best for it.

I don’t, I must say, see Greenwald launching rockets any time soon. The ideologue is still a long way from being the terrorist. These, though, are the first steps. Expelling doubt. Refusing contrariety. Hating play. Making oneself the human equivalent of a weapon, implacable, well aimed, reduced to a single function.