Nor can we, in ordering the argument, separate actual from apparent truth, since even the disputants are not certain about it beforehand.  Therefore I shall describe the various tricks or stratagems without regard to questions of objective truth or falsity; for that is a matter on which we have no assurance, and which cannot be determined previously.  Moreover, in every disputation or argument on any subject we must agree about something; and by this, as a principle, we must be willing to judge the matter in question.  We cannot argue with those who deny principles:  Contra negantem principia non est disputandum.

STRATAGEMS.

I.

The Extension.—­This consists in carrying your opponent’s proposition beyond its natural limits; in giving it as general a signification and as wide a sense as possible, so as to exaggerate it; and, on the other hand, in giving your own proposition as restricted a sense and as narrow limits as you can, because the more general a statement becomes, the more numerous are the objections to which it is open.  The defence consists in an accurate statement of the point or essential question at issue.

Example 1.—­I asserted that the English were supreme in drama.  My opponent attempted to give an instance to the contrary, and replied that it was a well-known fact that in music, and consequently in opera, they could do nothing at all.  I repelled the attack by reminding him that music was not included in dramatic art, which covered tragedy and comedy alone.  This he knew very well.  What he had done was to try to generalise my proposition, so that it would apply to all theatrical representations, and, consequently, to opera and then to music, in order to make certain of defeating me.  Contrarily, we may save our proposition by reducing it within narrower limits than we had first intended, if our way of expressing it favours this expedient.

Example 2.—­A. declares that the Peace of 1814 gave back their independence to all the German towns of the Hanseatic League.  B. gives an instance to the contrary by reciting the fact that Dantzig, which received its independence from Buonaparte, lost it by that Peace.  A. saves himself thus:  “I said ‘all German towns,’ and Dantzig was in Poland.”

This trick was mentioned by Aristotle in the Topica (bk. viii., cc. 11, 12).

Example 3.—­Lamarck, in his Philosophic Zoologique (vol. i., p. 208), states that the polype has no feeling, because it has no nerves.  It is certain, however, that it has some sort of perception; for it advances towards light by moving in an ingenious fashion from branch to branch, and it seizes its prey.  Hence it has been assumed that its nervous system is spread over the whole of its body in equal measure, as though it were blended with it; for it is obvious that the polype possesses some faculty of perception