When individual persuasion leads to social contagion

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The argument for banning smoking in public places was largely won on the basis of ‘passive smoking’. Once it had been shown that smoking was harmful to non-smokers, a convincing case could be made for a ban in the interests of protecting the innocent bystander.

Yet, the scientific evidence was far from watertight. Many studies had shown no link between exposure to second-hand smoke and ill health; indeed, more frustratingly for health campaigners, some even suggested that a non-smoker was slightly better off living with a smoker than in a smoke-free household. Although counterintuitive, this finding is not impossible – there are quite a few areas of human health where mild exposure to toxins is better than none at all.

Bluntly, the smoking ban was justified on the back of some rather dodgy statistical science – more ‘policy-based evidence-making’ than ‘evidence-based policy-making’. A few scientists dissented. Interviewed on Radio 4 late in life, Sir Richard Doll, who was among the first group ...