The other day , at our usual session where almost everything ( not every one) gets scrutinised, the conversation veered round to pleasant subjects like pollution, cancer, climate change etc. A friend mentioned the hazards of smoking and its close, well established links with cancer and other debilitating conditions this habit induces. Another one , a friend I mean, who is also an inveterate smoker protested and pointed out , according to him rightly, that 379 parts per million is the CO2 already in the atmosphere and it is the highest in 6,50,000 years. There will be a 5 degree celsius rise in global temperature by 2010 which will devastate about 20 % of the bio diversity. Besides, a host of lethal enzymes and juices are released into our system each time we get emotional or angry. Against all this the threat posed by smoking is negligible and hence he sees no reason to forego a habit that gives him so much pleasure. Now this argument will seem reasonably logical to a casual observer. I have mentioned this here only to show how such a stupid argument will seem to be very logical superficially. It would seem so even if it is pondered a little deeper. This is because the argument while it appears to have been intelligently thought out ,is devoid of one main ingredient - Common sense.Without common sense any argument becomes plain nonsense. A statement may have logic but if it has to be logical common sense must be there. Common sense is pragmatic intelligence based on sound principles of observation, judgement and practicability. A person who swears by logic alone and has no common sense is at best a fool and would be ready to walk into a stream to cross it because he had calculated the mean depth to be less than his height ! My friend belongs to this category. What can one do with a mind like that?