Once we have reinstated this distinction between words and violence, we might then move on to consider the question of how the one can lead to the other. This is perhaps the most compelling argument for restrictions on speech. If it can be determined that certain forms of speech incite violence, then there is a case to be made that responsibility is thereby shared between the perpetrator of the crime and the individual who provoked it.

The Rwandan genocide of 1994 is frequently cited in order to demonstrate a causal relationship between speech and vio­lence. The RTLM radio broadcasts that called on Hutus to “cut down the tall trees,” and described the Tutsi minority as “cock­roaches” and “snakes”—dehumanising language reminiscent of the Nazi propaganda that depicted Jews as rats—are said to be culpable in the stirring up of a maelstrom of hatred that resulted in the murder of almost a million people.

Incitement to violence has always been an offence under English common law, but the definition has also been open to subjective interpretation. At what point might we claim that a criminal’s individual responsibility is shared by those who inspired it, and how is this to be quantified? There is no human act that could not be said to have been prompted to a degree by some external influence, and there is no penalty for a criminal that might not be mitigated through appeal to extenuating circumstances outlined by a honey-tongued defence lawyer. This is why so many find the notion of personal responsibility intuitively reasonable; it has the effect of tidying up an otherwise messy business.