The country’s champions of free speech — the police — were recently out in force to ensure that the alt-right Trump-supporting Steve Bannon could address the student union in Oxford. The students, inevitably, wanted him silenced. But what were they so afraid of? Plato knew: it was a matter of the difference between the spoken and the written word.

In Plato’s dialogue Phaedrus, Socrates told a story that the Egyptian wise man Theuth was responsible for many inventions, but presenting them all to the king Thamus, he claimed that writing was the finest of the lot, ‘the magic key to memory and wisdom’. Thamus disagreed: writing would destroy memory, and therefore internalisation of learning. ‘Under you, students will read many things without being taught them, and so will appear to know a great deal. But for the most part they will remain in ignorance and difficult to teach, because they will have gained the appearance of wisdom, instead of the real thing.’

Socrates went on to say that writing reminded him of a picture: its products appeared alive, but ask them a question and answer came there none. So with words on the page: it looked as if they contained real ideas, but if you asked them a question in order to learn something, silence. ‘Once written down, words say exactly the same to those who know about the subject as to those to whom they are irrelevant… and if reviled or abused, they are incapable of defending or helping themselves.’

Only the to and fro of ‘living, animate speech’ between teacher and taught could plant the seeds of true knowledge that would flourish in the mind of the student. Hence Plato wrote dialogues — the closest he could get to the spoken word. And it is dialogue that is the students’ problem.

Fearless enough to read about the ‘fascist’ Bannon, because they can then revile or abuse him among their fellow-travellers without fear of reprisal, they are clearly petrified at the prospect of engaging with him live and in person and taking him on. After all, they might be persuaded! Or, even worse, made to look idiots! That would never do. So much safer to demonstrate their commitment to rational enquiry by shouting abuse.