THE HOME Secretary is in some ways an excellent politician. He shares with Jeff Rooker, the Agriculture Minister and hero of the airwaves this week, the distinction of knowing what he thinks and knowing why he thinks it, which makes him stand out in a sea of ministers parroting sound bites as they try to remember what they are supposed to be saying.

At least we know, then, where we stand with the Home Secretary. And much of what he says and does is admirable. But far too much is tinged with an illiberalism which assumes that the police and other agents of the state are always and everywhere a benign and error-free force.

Much of his speech yesterday was thoughtful, especially its concern to deal with the real corrosion of quality of life, which is the fear of crime rather than disorder itself. But his comments on the "walk on by" society, however well-intentioned, were unwise. This may be a telling commentary on the present state of public incivility, but his suggestion that people should "intervene" when they see a group of 11- or 12-year- olds vandalising a telephone box was unrealistic. The reason why most people do not take the law into their own hands in such situations is that they are too well aware of the risks of violence, with or without the use of weapons. It is all very well for Stalwart Straw to boast about his citizen's arrests and his rugby-tackling of fleeing thieves. Most women and old people, quite sensibly, would not even consider asking someone politely not to smoke on a train.

It is not surprising that senior police officers contradicted him, urging people not to intervene but to call the police and be prepared to give evidence in court - important civic duties that are also neglected, and to which Mr Straw could more usefully have addressed himself.

At the heart of Mr Straw's folly is the slippery slope argument, which is just as much a fallacy whether the slope is from soft drugs to hard, or from dropping litter to petty crime. "Zero tolerance" is a fine slogan but a hopeless policy; police resources and time have to be prioritised. If every public display of high spirits or of minor disrespect for authority were treated as the beginning of a career in crime, we should all soon find ourselves under surveillance.

Many people - perhaps especially those young enough not to remember them - feel mournfully nostalgic for the days when pensioners could tick off a 15-year-old and be respected because they knew them, or were related to them. And there is much wrong with the coarseness, rudeness and unloveliness of many of our fellow-citizens' public behaviour. But the idea of self- appointed Jack Straws bossing everyone about and marching people they do not like the look of down to the police station would be far from an improvement.