pothesis; as (happens) to those who say that a vacuum, and a plenum of air, are the same, since it is clear that if the air should depart, there will not be a less, but a greater vacuum, yet there will no longer be a plenum of air. Hence, a certain thing being supposed, whether false or true, (it makes no difference,) one of them is subverted, but the other not, hence they are not the same.
In a word, from those things which are in any way predicated of each, and of which these are predicated, we must consider if there be any discrepancy; for whatever are predicated of the one, ought likewise to be predicated of the other, and of which the one, is predicated, it is necessary that the other also, should be.
Besides, since the same thing is predicated multifariously, examine whether after some other mode they are the same, since it either is not necessary, or not possible that those which are the same in species or genus, should be the same in number, but we will investigate whether they are the same in this way, or not in this way.
Again, whether the one can possibly be without the other, for they would not be the same.
Chapter 2
The places then pertaining to the same thing, are said to be so many, but it is clear from what has been stated, that all places belonging to the same thing, which are subversive, are useful also to definition, as was observed before; for if both the name, and the definition, do not denote the same, it is evident that the proposed sentence will not be a definition. On the other hand, none of the confirmative places is useful to definition, since it is not sufficient to show that what is under
