Banning things that are bad for us is not a good idea
Should people smoke in cars? No, they should not. When I see a motorist with a cigarette in their hand, I suspect they don't have their full attention on the road. You automatically think a little less of a person smoking at the wheel.
Should people smoke in their cars when there are children present? Absolutely not. It is obvious that it is bad for the tender lungs of young children to have tobacco smoke blown their way.
However, should smoking in cars be banned by law - as health minister Edwin Poots proposes? That's another question altogether - and it touches on a great misunderstanding of our time.
There is a difference between what is illegal and what is immoral; what is illegal and what is unedifying. Or what is illegal and what is bad for you.
The whole silly business of 'political correctness' arose because there was confusion between good manners and censorship.
It is bad manners to call someone a rude name. Disabled people feel demeaned by the word 'cripple'. So we do not use that word out of consideration for the disabled person.
But you don't go from this politesse to banning the word 'cripple', or banning any other word, either.
Behaviour can be - and often is - changed by social mores, by public education and even by stigma.
Stigma is one of the main reasons why people often stop smoking. They are willing to take the risk with their health but, at the end of it all, they can no longer stand the stigma of being a cigarette smoker. They get fed up of being sent out to the garden, or the street corner, to have a fag.
Some things do need to be regulated by law - banking comes to mind. But not every aspect of human conduct needs a law to regulate it.
Regulating everything by law is not only bossy and authoritarian and gives more political power to the political class: it can cause problems with policing the law.
How is the proposed law banning smoking in cars to be policed, for instance, when the law against using mobile phones in cars is already blatantly flouted? Haven't the police enough to do already?
This proposal, frankly, is Soviet Union ideology. There has to be a limit to the powers that the law can have over our civil and personal lives. The upcoming area of concern over health is now obesity. We consume far too much sugar and fat these days, while leading more sedentary lives. One-in-four girls and one-in-six boys in Primary 1 in Northern Ireland is now obese, or overweight, and there is a prediction that we face a diabetes epidemic.
Does that mean the law should ban hamburgers and ice-cream? Or police private homes and cars to see what people are eating? Snatch sweets and crisps from the hands of babies?
It could happen.
As I am no sylph myself, I am in no position to pass judgment on this matter. But to those doctors who advocate moving from introducing laws against smoking to suggesting a war against obesity, there will surely be those who respond: Physician, cure thyself.