Every adult who has looked after children will therefore feel deeply for the parents of two-year-old James Bulger, who was abducted on Friday afternoon from a shopping centre in Bootle and later brutally murdered. It was for less than a minute that his mother's attention was elsewhere, and there is no suggestion that she acted irresponsibly.
Perhaps that is why this seems poised to be one of those crimes that prompts a great outpouring of public sympathy. The mechanism with which most people defend themselves against thinking of being the victim - to say simply: 'It couldn't happen to me; I'd be more careful' - does not apply here.
The shadowy video images now being studied by the police add poignancy to the story. The child is seen walking off with two older boys, his trusting hand reaching up to grasp one of theirs. What happened between then and the discovery of James's mangled body on a railway line on Sunday afternoon is not yet clear. But it was not nature or capricious fate that ended his life: it was human evil.
It is no comfort to be told by experts that the average Briton has more chance of being killed on the road than by all the murderers and psychopaths still at large, or that violent crime probably remains less common than it was when our great-grandparents were children. James's murder will make people put less trust in those they do not know. Fewer parents will allow their children to play in the street, to take the bus alone to school, to go out for a pint of milk after dark.
Anyone tempted to dismiss such things as trivial should remember that it is often the details that make cities tolerable or intolerable to live in. In Tokyo, suburban underground stations still keep racks of umbrellas for passengers to borrow on rainy nights and bring back in the morning. New Yorkers, by contrast, have taken to leaving 'No Radio' signs in their parked cars, and carrying a dollars 50 bill with them at all times for fear of being attacked by a drugged mugger who will not believe that they have only small change.
At least one good thing may come out of the grim work now being done by Merseyside police: people are likely to be less hesitant when they see a child wandering alone. With the uncomfortable memory of those pictures showing young James Bulger wandering, ignored, around the shopping precinct, more will come forward to help lost children in future. Tragedies like this will undoubtedly happen again; but a young life or two may be saved.