1. A common pattern in the discussion on the usefulness of a theory is the following. The sceptic narrows down the theory to some statements taken from, at best, a textbook or, at worst, the newspapers and then shows that this theory has no empirical validity. The case for the defence amounts to widening the theory, making it more general, and trying to show that this generalized theory is consistent with the facts. In the limit the theory has become so general that it has lost all predictive power. The discussion is made lively by accusations of unfair representation, lack of understanding, logical inconsistency, conservatism, iconoclasm. Happily, it is only ink that flows and not blood. The whole affair is rather sterile, but so are other pastimes of less scientific nature.