The article on the dangers of drugs published yesterday by Professor David Nutt is a welcome development in the drugs debate, but I am afraid that it may be a false dawn for people who want to liberalize drugs. The crux of the article is that alcohol has a greater social cost than most drugs, and that certain Class A drugs like ecstasy are less harmful to users than legal drugs like tobacco and alcohol. This is welcome ammunition in the fight to liberalize drug laws, but relying on it heavily may leaves the pro-liberalization side exposed.

Most people know that ecstasy and the like are less dangerous than alcohol. To have a widely-respected public figure like Prof Nutt saying so, and being publicized widely in the media, is a very good thing and a step towards destigmatizing open discussion about drugs. This open discussion is needed so we can have a clear, level-headed debate about drugs and an acceptance that people must be free to make their own choices even if those are bad choices. The article is a useful demonstration that the dangers of drugs compared with legal substances are not clear-cut, and not something that the state should try to make blanket bans on.

The problem is that using expert testimonies like that of Prof Nutt is playing with fire. Yes, this article shows that drugs are not unequivocally harmful compared with alcohol and tobacco, but that is only a part of the argument for legalization – the other part being that the state should not make laws to protect adults from themselves. This is the part that is motivated by a love of liberty, rather than a technocratic harm reduction analysis.

The liberal side of the pro-legalization argument is fundamental to belief in a free society – that adults should not be treated like children. Many things carry risks and benefits, and the cost benefit analyses involved in choosing which to use and which to reject is a personal, subjective one.

My worry is that embracing Prof Nutt too closely will undermine the philosophical argument for drug legalization, and leave liberals and libertarians vulnerable to changes in Prof Nutt’s calculations about harm causation. I welcome this article, and I’m encouraged by the ripples it has made, but at best it is a small part of a much bigger argument.