Now persuasion is a sort of demonstration (since we are most fully persuaded when we consider a thing to have been demonstrated); the orator's demonstration is an enthymeme, and this is, in general, the most effective of the modes of persuasion the enthymeme is a sort of deduction (the consideration of deductions of all kinds, without distinction, is the business of dialectic, either of dialectic as a whole or of one of its branches): clearly, then, he who is best able to see how and from what elements a deduction is produced will also be best skilled in the enthymeme, when he has further learnt what its subject matter is and in what respects it differs from the deductions of logic.