I want to argue that false philosophy can be dangerous, and to suggest that, if circumstances prevent its being refuted in print, it is probably all right, in extreme cases, to try to silence it in other ways. I shall take as my example a philosophy that can be contrasted with humanism and that I shall call “personism.” But first a few remarks about the influence of philosophy in general.

In Book 1 of his Treatise on Human Nature, David Hume writes that “errors in religion are dangerous; those in philosophy only ridiculous.” F. H. Bradley, on the other hand, says in Ethical Studies that “the man of mere theory is in the practical sphere an useless and dangerous pedant.” It is quite possible that Hume was being ironical. Leaving that aside, though, it seems to me that his thesis is wrong, whereas Bradley’s has more than a grain of truth in it. Hume’s thesis is wrong, firstly because there is no general reason why an error could not be dangerous as well as ridiculous, secondly because some doctrines are both philosophical and religious, and so on his own showing can be both ridiculous and dangerous. And, thirdly, Hume thinks bad philosophy is harmless because he holds that human reason is inactive. If this were so then good philosophy, and religion, and science would be just as ineffective as he takes bad philosophy to be. But that can’t be right.

In August 1991 Peter Singer