My sharp-eyed son saw something suspicious in the Coco Before Chanel poster. The lovely French actress Audrey Tatou is sitting with a speculative pen held up at shoulder height and has an open diary in her lap.
But there was something in the curl of Tatou's fingers that didn't seem quite literary. "I bet it was originally a cigarette," he said, "and they've added the book." And when you track down the original version of the poster, so it proves to be.
In French, the woman was smoking a cigarette. She was like that, Coco Chanel. She slept with Nazis and smoked cigarettes. In her defence of one charge she said that her "coeur" was French but her "con" was international (it isn't quite as rude as the English translation, incidentally). But she had no defence against the other charge. In those days she didn't need one. But that was then.
Now she is a role model for millions of women. She glamorises smoking. If she is shown with a cigarette, she becomes an advertisement. She makes a small but perceptible increase to the number of young women who will take it up.
It creates a holocaust every year. Worldwide, 50m people are going to be killed by cigarettes in the next decade. And what cruel deaths they will be.
Liberals have no answer to this. They can only put up an abstract argument about freedom of choice against the physical facts of mass addiction and death.
The logic of care is implacable. The state must not endorse the mass killing of its citizens. It must do everything it can to stop the evil.
Images that glamorise smoking should be banned. Smoking in public should be banned. Smoking in council housing should be banned. There's no reason why it shouldn't be.
I don't agree with any of this but I haven't got any arguments against it. As the human spirit evolves there may well come a time when smoking is generally regarded as unpleasant a habit as genital mutilation. For the time being, it's quite popular.
If there's no arguing with it, let's look at another area of belief and apply the same logic.
If you believe in God and the reality of heaven, then religion will be by far the most important thing in life. It will change your attitude to death itself. No material discomfort will weigh against an eternal life of bliss for those who behave properly on earth. You will also understand that people who don't agree are hurting more than themselves. Their defiance will lead others down a path of damnation.
How can their rights be given equal weight to the eternal life of your children?
Wilful unbelievers will create a trillion millennia of pain for billions of souls. Anything is better than that. Therefore – and there's no arguing with this – holy war is the single most important activity for anyone who genuinely believes in God.
You can't get round that logic. But if we're going to agree to differ on smoking, jihad, educational opportunities, carbon footprints, diversity, social exclusion ... we're going to need a new way of proceeding. I've no idea what that is or how it will come about. But logic will be a false friend.