Some years ago, when I was receiving what seemed to me alarmingly large sums of money for addressing business conferences and the like, I used to teach rhetoric. We may first think of rhetoric as an art (which it is), but it is also a science, in the sense that it has procedures and techniques which can be evidenced empirically. It has been studied from at least the time of the ancient Greeks. Even Aristotle wrote a (rather tedious) book on it.

The most accessible example is “Friends, Romans, countrymen” from Act III of Julius Caesar. Ironically, we do not know whether Shakespeare himself ever experienced those heady moments of holding and controlling the feelings of a large audience. If not, it was only his genius which enabled him to exemplify rhetoric so brilliantly.

Mark Antony is addressing a lynch mob which is passionately against the assassinated Caesar. And that key first line forces them to recognise that he is one with them. We do not dislike “people like us”; it’s written in our genes. But before they can analyse that, he counters their suspicions by assuring them that he is not going to praise that vile Caesar. Nor, they discover quickly, is he going to attack their hero, Brutus. On the contrary, Brutus is an honourable man.

In fact he is so honourable that Antony is called upon to mention this several times. But each time he couples it with a fact which is incompatible with the claim of an honourable man. The compliment becomes a condemnation. Beware when your opponent assures his respect for your good faith.

But since I can only exemplify, I move on to the point where Antony is overcome by his depth of feeling: “Bear with me; my heart is in the coffin there with Caesar, and I must pause till it come back to me.” You can almost hear the crowd gulping in emotional sympathy, just as we do when we hear an appeal from a parent on the television. And on some occasions it comes from the very parent who has done the dirty deed. Antony times it to perfection. During the space he has created with his crocodile tears the crowd begins to wonder whether he has a point.

And then he strikes. He reveals that he holds Caesar’s will in his hand, but he does not intend to read it although it is so generous to them that they would kiss Caesar’s wounds in gratitude if they heard it. And predictably they insist, they implore, they demand that he should do so. But to refuse to read the will because its generosity might inflame them is high-level provocation, and Antony sustains it.

Instead, he asks their permission (for he is of course no more than their servant) to show them the body of Caesar, wound by wound. “If you have tears prepare to shed them now.” An appropriate visual aid can be invaluable for dramatic and persuasive effect. I always look for an opportunity to use one, but I rarely have to hand a bloodstained corpse. No wonder he is able to say: “O, now you weep, and I perceive you feel the dint of pity.”

The crowd is so enraged it is on the point of riot. They have even forgotten the existence of the will. But Antony wants a rebellion, not an episode of temporary vandalism. He must push the message fully home. He reads them the will and the public benefits it contains. And the mob rushes off intent on destruction. While Antony, presumably with a little self satisfied dimple in his cheek, says: “Now let it work; mischief, thou art afoot.”

Was Mark Antony insincere? At a deeper level we have no reason to doubt his love for Caesar, and his determination that his treacherous assassins should be punished. And if he sees that a resulting coup will create a new regime in which he will be a leading participant, that is hardly surprising.

But the speech itself is a brilliant exercise in persuasive communication; and his last line would show that, even if it were not obvious from the context. And yet he has the nerve to say: “I am no orator as Brutus is; but, as you know me all, a plain, blunt man.” What a decent chap! No wonder he gets later to rule Egypt from Cleopatra’s bed – even if the long-term outcome proved unsatisfactory.

We have at least two considerations to reflect on here. The first is to consider whether good rhetoric is intrinsically dishonest. And that analysis might start by investigating the elements of rhetoric which most of us use naturally.

If you have ever smiled at someone in order to get good service, that’s rhetoric. If you have ever said “thank you” when you didn’t mean it, that’s rhetoric. If you have ever chosen your words, or the order of your words, to give a specific impact to your communication, that’s rhetoric. And it can prove dangerous when your public remark is belied by your private views – as many politicians have had cause to discover. As did Tony Hayward, chief executive of BP, when he unwarily said: “I want my life back.”

The second is to be on guard against the rhetoric we hear – from the political broadcast to a Science and Faith column to a papal statement. Again, I would not suggest the Pope was ever insincere, but his addresses are constructed to give a particular effect, and we need to know how our susceptibilities are being addressed. I bear in mind that his hero, Socrates, continually championed the truth while using the most skilful rhetoric with which to bolster his, often doubtful, arguments.

Is rhetoric simply a form of manipulation? Is it the duty of the Christian always to speak plainly, and from the heart? And how would our social life change if that were so?