 Liberals tend to justify freedom generally, and free speech in particular, for a variety of reasons. According to Mill, free speech fosters authenticity, genius, creativity, individuality and human flourishing. He tells us that if we ban speech the silenced opinion may be true, or contain a portion of the truth, and that unchallenged opinions become mere prejudices and dead dogmas that are inherited rather than adopted. These are empirical claims that require evidence. Is it likely that we enhance the cause of truth by allowing hate speech or violent and degrading forms of pornography? It is worth pondering the relationship between speech and truth. If we had a graph where one axis is truth and the other is free speech, would we get one extra unit of truth for every extra unit of free speech? How can such a thing even be measured? It is certainly questionable whether arguments degenerate into prejudice if they are not constantly challenged. Devil's advocates are often tedious rather than useful interlocutors. Sometimes supporters of free speech, like its detractors, have a tendency to make assertions without providing compelling evidence to back them up. None of this is meant to suggest that free speech is not vitally important: this is, in fact, precisely the reason we need to find arguments in its favour. But regardless of how good these arguments are, some limits will have to be placed on speech. 