Simon Blackburn: The important thing about dishonesty is that we should try to be honest about it

I am not an enormous fan of questionnaires. Even questionnaires about trust may, or may not, be trustworthy. A self-report, for instance, about one's honesty might get one answer at one time, and a very different one a little later.

Feeling a little like Jack the lad, you may brag that you do not mind bending the rules a bit. But righteously smarting from someone else's villainy, you naturally protest that you are incapable of anything like that, as honest as the day in fact. I do not know whether this kind of variation explains the astonishing jump (in one of the two surveys that lay bare Britain's "integrity crisis") in people saying they would "trust someone like themselves", from 35 per cent a year ago to 60 per cent at present. But the finding is as telling, and as ambiguous, as the more negative statistics highlighted above.

Since our expectations of others are formed by imagining ourselves in their shoes, this is either a heart-warming nationwide improvement or a proof that the Edelman "trust barometer" needs a hefty tap.

There are also questions of interpretation to be clarified. Asked if something is never justified or rarely justified, are we allowed to gravitate to strange scenarios? Take, say, drunken driving. Very bad, of course; absolutely wrong in nearly all circumstances; but never? Well, let's suppose your partner is the designated driver, and you are only a little tipsy. As arranged, your partner drives off, and promptly suffers what you know is a serious heart attack. Every second counts; the hospital is five minutes away, the roads are empty, you have no mobile... Even principles have exception clauses.

The only brand-name philosopher who thought otherwise was Immanuel Kant, who conceived it to be your duty to tell the mad axeman where your children are sleeping if you cannot wriggle out of answering him. This raised eyebrows even in his own day.

Classical philosophers hoped to be able to show that virtue aligned with personal well-being or flourishing. It would be nice if this were true, but in far too many circumstances it isn't, unless like Kant you posit an afterlife where all accounts are balanced. In the real world villains certainly appear to flourish, although the pious amongst us may hope that deep down they do not sleep easy.

It is better to realise it is a social and political achievement to make sure that honesty and trustworthiness are in peoples' own interests. Not, however, an achievement that bankers, policemen, MPs, prime ministers, journalists, or even priests are out to protect. That would sound too much like public service – and nobody in their right mind believes in that any more.

Simon Blackburn is Professor of Philosophy at the University of North Carolina