Don't tell lies. But don't tell untimely truths either

When the journalist Camilla Long picked up the Hatchet Job of the Year award on Tuesday, after laying into Rachel Cusk's account of her marital breakdown, Aftermath, she came to the defence of honesty, however painful. Fellow hatchetmen- and women, she said, were not being cruel, but observant. "It is much easier to be nice … and talk about kittens," she told the Today programme, in a week when belief was being tested in supermarkets and courts of law. And it is true that if most people were not honest about most things most of the time, society would fall apart. This is because trust is the chief form of social glue: we have to trust people to do what they say they will do, to keep the great majority of their promises, and to fulfil their obligations. If labels say "beef" while laboratories say "horse", and if, as an Ipsos MORI poll on Friday suggested, 70 per cent of people do not "generally trust MPs to tell the truth", it becomes a common view that dishonesty and unstrustworthiness are widespread in society. But this is not so.

The proof lies in the existence of streets and houses, public transport services, water and electricity supplies, stocks on the shelves in shops – all these things, which we take for granted, are there because most people have indeed been honest: they have entered into undertakings with one another, cooperated, and done what they said they would.

Dishonesty gets into the newspapers because the most harmful forms of it are, relatively speaking, rare. Crime and fraud are destructive, and small amounts of each can do a great deal of harm. People in important positions of trust who betray the confidence placed in them – MPs, judges, CEOs of companies, carers of children and the elderly – are targets of special opprobrium when they fail because of dishonesty, and rightly so.

But it is also the case that dishonesty can be a useful thing, when in constructive ways it acts as a social emollient, and a servant of higher and better kinds of truth or goodness. As the Church of Scotland cannily says, "It is a sin to tell an untimely truth." Classic cases are those in which a diplomatic answer is returned to the query, "Does my bum look big in this?" and when the French farmer is asked by the Gestapo if he has a British airman hiding in his barn. Lies are here told, but on the right side of dilemma. Would we be so inflexible – as George Washington allegedly was – that we would tell the truth no matter what harm might follow?

If one could be an invisible presence at a cocktail party, equipped with knowledge of the true state of each guest's attitudes and feelings, one would be in a sea of dissimulation. "I'm very well, thank you!" "How lovely that dress is!" "How delightful to meet you!" "Let's have lunch some time!" If the air could turn a darker shade of blue at each little lie and each act of pretence, it would quickly become opaque.

We all know this, and yet we discount it. We even appreciate the courtesy shown, the consideration given, by these harmless and constructive misdirections from truth, because they lubricate social interaction and make good things possible – as when, among all those we would not mind not seeing again, we encounter someone who becomes important to us.

But obviously we are on difficult terrain here. To justify an act of dishonesty on the grounds that it does more good than harm does not stand up on closer scrutiny. Two constraints apply: conscience, and the consequences of being found out. It is the latter that most tends to govern people's behaviour; the former is an elastic commodity, and can bend and stretch a long way when confronted with the urgencies and emergencies of life.

Plato wished to banish poets from his ideal Republic on the grounds that fiction consists, by definition, of assertions about what did not happen, for he demanded that only truth can ever be permitted. Leaving aside the question of what a society would be like that had no theatre, no song, no stories and legends to entertain, enlighten and inspire, Plato's republic would be a very comfortless place, because honesty can be, and too often is, an abrasive commodity in those marital bedrooms and those cocktail party lounges where, in our own more sensible world, dishonesty finds a useful place. An honest remark that devastates someone, cutting them to the very bone – and worse, which makes the utterer feel mighty self-righteous in being so sterling a servant of truth – is thus a double sin in a world where life is enough of a challenge already.

To make use of dissimulation and "little white lies" in cases where they do good is not inconsistent with being an honest person. In fact, almost all honest people would confess to the occasional dishonesty along the lines mentioned. Some of them might even confess to quite big dishonesties, which they practised in the hope of preserving something of real value (their marriages, say) or of protecting people they care about. These are indeed justifications and merit being respected for their intention; though the recipients of these kindly falsehoods are unlikely to think so when they find out.

It goes without saying that the justification for such dishonesties has to be a good one, and there are few general rules to guide us: the decision to speak truth, to withhold truth, or to tell an actual untruth, has to be case by case. Consider the following circumstance: one's elderly and now rather confused parent has fallen suddenly ill, and the doctors detect a serious and indeed fatal underlying condition. Should one tell one's parent this? Might it be better to say nothing, or even to offer reassuring untruths? Why cause unnecessary distress, and with it greater vulnerability to the condition in question? In the case of a robust individual who values her autonomy and wishes to know how things stand, dishonesty would be doubly wrong – because it is dishonesty, and because it deprives that individual of her autonomy.

The Church of Scotland's pertinent dictum apart, truth and honesty are great goods and their opposites have disproportionately bad effects.One attempted shoe-bomber on a flight submits millions of the rest of us to the irritation of having to find socks with no holes when we are late for the airport.

This makes us think that we live in a world haunted by crooks and deceivers. And that pours money into the pockets of the security industry: locks and bars and gates and CCTV cameras and encryptions and pin numbers and long queues at airports and additional insurance premiums – think of the burden placed on society by the few who are genuinely and seriously dishonest. The effect they have is to force us into thinking that honesty is unprofitable, that the bad thrive at our expense, that you cannot really trust anyone.

The living proof of the opposite is all about us, in the functioning of our cities and the order of our lives. But as we hunker down into our suspicious attitude that dishonesty is rife, we come to overgeneralise. Take politicians: as a class they are thought to be writhing bags of dishonesty and dissimulation, out to get us, no further to be trusted than one can throw an elephant. The intractable nature of government – which is like trying to herd huge numbers of cats – forces compromises, difficult decisions, U-turns and fudges on politicians, and every political career is doomed to failure for the reason that it can never, in the end, appear honest.

To say that there are some politicians who honestly have to dissimulate or compromise, or whose intentions were honest but the exigencies turned those intentions awry, is to seem to make excuses for them, for they are among the very first from whom honesty is demanded. We would be naive not to recognise that they are going to have a tough time responding to our demand for their honesty: which is not a reason for us not to demand it. The Church of Scotland's dictum applies far less to them than to the rest of us.