Book, Paragraph

1      I, 15| pronounced false. These are valid witnesses to the fact that
2      I, 15|  not the case; they are not valid witnesses to the quality
3     II, 22| since they do not represent valid syllogisms. Having made
4     II, 24|     which, again, yields no valid proof. Thus, it might be
5     II, 24| man-there is, of course, no valid proof here; not every vicious
6     II, 25|     Sign can form part of a valid logical proof.~(3) Enthymemes
7     II, 25|     that they do not form a valid logical proof: this, too,