I once knew a doctor, a pretty ordinary doctor, except that he used to write for medical and other journals. One article he wrote was to query the use of homeopathic remedies, which have for quite a long time been popular in America.

The point he insisted on most strongly was this: defenders say that, in the worst case, homeopathic remedies, cannot do any harm. The dilutions of active ingredients are so extreme that you would drown in homeopathic remedies long before you got anything like an overdose. With standard remedies, on the other hand, it is quite easy to take an overdose, whether by accident or on purpose. Quite a lot of people get sick or sicker because of inaccurate or inappropriate mainstream medication.

My friend agreed with this, but he went on to say that in his view it was an argument against homeopathy. He said that if all this was true, and if homeopathic remedies were of use, they were unlike anything else in the physical world – or indeed, mental or cultural worlds – which we know of.

Whenever we find something that has a power, that power can do good or can do harm. It does good if it is used in the right way at the right time, harm if it is used in the wrong way or at the wrong time. Even your own physical health and strength can be used in ways which are, or may be, harmful to you or to others. I am never going to be killed by an accident when doing extreme snow-boarding, not because I'm too smart, but because I'm not strong enough to get out there on the board. My weakness protects me from the harm that my strength might bring me.

Now, I am not really interested in homeopathy or in snowboarding, but I do want to say I think my friend was right about power in general: power is two-way. What does good can do harm. And I want to apply this to some stupid things that are sometimes said in debates about censorship or control of literature, television, the internet. Without going very deep into the debate, or trying to solve it, I want to draw attention to something stupid which we ought to avoid.

People sometimes talk as if it was impossible for a book, or a film, or a TV program, or a video game, to do any harm. They talk this way especially about "high art" books or images which have had some real thought put into them, perhaps, and which appeal to experts. Salman Rushdie's book The Satanic Verses was one of these, and so were the images of religious items in buckets of urine that appeared a few years ago. The experts insisted that these works of art should be judged independently of people's reactions, of their social value, and of the possible harm they might cause.

What I want to say is: the experts can't have it both ways. If they also insist that these works of art are in some ways good, that they are of value to people or in themselves, they have power. And if they have power to do good then they have power to do harm. This applies to movies, the internet and TV as well.

All these things have power for good, which means that they also have power for harm: and this means that we should think about how we can help them to do good and avoid their doing harm.

Christopher Martin teaches philosophy at the University of St Thomas in Houston, Texas. Email: martincf(at)stthom.edu