Chapter 12
An argument is most clear in one way, and that the most popular, if it be so concluded, as to require no further interrogation; but in another way, which is especially said to be, when things are assumed, from which (the conclusion) necessarily results, but (the argument) concludes through conclusions; moreover, if there is any thing deficient, of what is very probable.
Again, an argument is called false in four ways; one when it appears to conclude, yet does not do so, which is called a contentious syllogism; another when it concludes, indeed, that which does not pertain to the proposed (problem), and this happens especially in arguments leading to the impossible; or it concludes pertinently to what is laid down, yet not after an appropriate method, and this is when a non-medical argument appears medical, or the non-geometrical to be geometrical, or the non-dialectic to be dialectic, whether the result be false or true. Another way, if it concludes through falsities, and of this the conclusion will be sometimes false, and sometimes true, as the false is always concluded through falsities, but it is possible that the true may be so even from things not true, as was said also before.
That the reasoning, then, is false, is rather the fault of the arguer than of the argument, and neither is it always the fault of the arguer but when it escapes him, since of many truths per se, we admit rather that, which from things especially appearing (probable), subverts something true. For such (reasoning) is a demonstration of other truths, as it is requisite that some one of the positions should not altogether be, so that there will be a demonstration of this; but if it should conclude
