Chapter 1
In how many figures, through what kind and number of propositions, also when and how a syllogism is produced, we have therefore now explained; moreover, what points both the constructor and subverter of a syllogism should regard, as well as how we should investigate a proposed subject after every method; further, in what manner we should assume the principles of each question. Since, however, some syllogisms are universal, but others particular, all the universal always conclude a greater number of things, yet of the particular, those which are affirmative many things, but the negative one conclusion only. For other propositions are converted, but the negative is not converted, but the conclusion is something of somewhat; hence other syllogisms conclude a majority of things, for example, if A is shown to be with every or with a certain B, B must also necessarily be with a certain A, and if A is shown to be with no B, B will also be with no A, and this is different from the former. If however A is not with a certain B, B need not be not present with a certain A, for it possibly may be with every A. This then is the common cause of all syllogisms, both universal and particular; we may however speak differently of universals, for as to whatever things are under the middle, or under the conclusion, of all there will be the same syllogism, if some are placed in the middle, but others in the conclusion, as, if A B is a conclusion through C, it is necessary that A should be predicated of whatever is
