Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
I have therefore no hesitation in calling the following forms of argument also consequential, although they argue from the past to the future: some however divide them into two classes, those concerned with action, as in the pro Oppio,
How could he detain against their will those whom he was unable to take to the province against their will?and those concerned with time, as in the Verrines, [*](Verr. I. xlii. 109. The praetor on entering office on Jan. I issued an edict announcing the principles on which his rulings would be given. This edict was an interpretation of the law of Rome, and held good only during the praetor's year of office. )
If the first of January puts an end to the authority of the praetor's edict, why should the commencement of its authority not likewise date from the first of January?
Both these
So too I feel clear that we should rank as consequential arguments those derived from facts which lend each other mutual support and are by some regarded as forming a separate kind of argument, which they [*]( Ar. Rhet. II. xxiii. 3. ) call ἐκ τῶν πρὸς ἄλληλα, arguments from things mutually related, while Cicero [*](de Inv. I. xxx. 46. ) styles them arguments drawn from things to which the same line of reasoning applies; take the following example [*](ib. 47. ) :
If it is honourable for the Rhodians to let out their harbour dues, it is honourable likewise for Hermocreon to take the contract,or
What it is honourable to learn, it is also honourable to teach.Such also is the fine sentence of Domitius Afer,
which has the same effect, though it is not identical in form:
I accused, you condemned.Arguments which prove the same thing from opposites are also mutually consequential; for instance, we may argue that he who says that the world was created thereby implies that it is suffering decay, since this is the property of all created things.
There is another very similar form of argument, which consists in the inference of facts from their efficient causes or the reverse, a process known as argument from causes. The conclusion is sometimes necessary, sometimes generally without being necessarily true. For instance, a body casts a shadow in the light, and the shadow wherever it falls indicates the presence of a body.
There are other conclusions which, as I have said, are not necessary, whether as regards both cause and effect or only one of the two. For instance,
the sun colours the skin, but notv4-6 p.247everyone that is coloured receives that colour from the sun; a journey makes the traveller dusty, but every journey does not produce dust, nor is everyone that is dusty just come from a journey.
As examples of necessary conclusions on the other hand I may cite the following:
If wisdom makes a man good, a good man must needs be wise; and again,
It is the part of a good man to act honourably, of a bad man to act dishonourably,or
Those who act honourably are considered good, those who act dishonourably are considered bad men.In these cases the conclusion is correct. On the other hand,
though exercise generally makes the body robust, not everyone who is robust is given to exercise, nor is everyone that is addicted to exercise robust. Nor again, because courage prevents our fearing death, is every man who has no fear of death to be regarded as a brave man; nor is the sun useless to man because it sometimes gives him a headache.