The promise of classical rhetoric is that, if we succeed in mastering the ars rhetorica, we shall be able to speak and write with complete persuasiveness. We shall be able, that is, to shift or move even a hostile or sceptical audience towards the acceptance of our point of view. But it remains for the rhetoricians to explain how this can be done. What are the specific techniques that enable us to speak and write in a ‘winning’ style? This is the question with which the following three chapters will be concerned.

THE INVOCATION OF COMMONPLACES

According to the classical rhetoricians, certain types of argument may be said to possess an inherently persuasive character. The first task of the orator is to find them out (invenire) and learn how to apply them in individual cases. This is the contention examined by the Roman theorists of eloquence under the heading of inventio, which in turn explains why they invariably insist that, as the Ad Herennium puts it, ‘among the five tasks of the orator, the mastery of invention is both the most important and the most difficult of all’.

Some arguments are not in this sense ‘artificial’; they are not dependent, that is, on the art of rhetoric for their persuasiveness. Aristotle originally introduced this terminology in book I of the Rhetoric, in which he contrasts (in Hobbes's rendering) ‘Artificial Proofes’ with ‘Inartificiall Proofes, which we invent not’.