Putting the finishing touches to an editorial some years ago, I decided at the last minute that “Wanted: guidelines that doctors will follow” was a better title than “Wanted: doctors who will follow guidelines.” My thinking was that doctors aren’t automata. You can’t just write a few lines of code to achieve the desired outcome; human beings are more complicated than that.

I wish I’d gained further insight into behavioural change since that midnight revelation, but I haven’t. Ruminating on the difficulties of getting people to do the right thing, I console myself with Immanuel Kant’s claim that “Out of the …