14. Also, any two universal propositions, of which the terms of the one (that is, the subject and predicate) are to the terms of the other, and their order inverted, as these, _every man is a living creature_, and _every thing that is not a living-creature is not a man_, are _equipollent_. For seeing _every man is a living creature_ is a true proposition, the name _living creature_ contains the name _man_; but they are both positive names, and therefore (by the last article of the precedent chapter) the negative name _not man_, contains the negative name _not living-creature_; wherefore _every thing that is not a living-creature, is not a man_, is a true proposition. Likewise these, _no man is a tree_, _no tree is a man_, are _equipollent_. For if it be true that _tree_ is not the name of any _man_, then no one thing can be signified by the two names _man_ and _tree_, wherefore _no tree is a man_ is a true proposition. Also to this, _whatsoever is not a living-creature is not a man_, where both the terms are negative, this other proposition is equipollent, _only a living creature is a man_. [Sidenote: Negative propositions are the same, whether the negation be before or after the copula.] 15. Fourthly, negative propositions, whether the particle of negation be set after the copula as some nations do, or before it, as it is in Latin and Greek, if the terms be the same, are equipollent: as, for example, _man is not a tree_, and, _man is not-a-tree_, are equipollent, though Aristotle deny it. Also these, _every man is not a tree_, and _no man is a tree_, are equipollent, and that so manifestly, as it needs not be demonstrated. [Sidenote: Particular propositions simply converted, are equipollent.] 16. Lastly, all particular propositions that have their terms inverted, as these, _some man is blind, some blind thing is a man_, are equipollent; for either of the two names, is the name of some one and the same man; and therefore in which soever of the two orders they be connected, they signify the same truth. [Sidenote: What are subaltern, contrary, subcontrary, and contradictory propositions.] 17. Of propositions that have the same terms, and are placed in the same order, but varied either by quantity or quality, some are called _subaltern_, others _contrary_, others _subcontrary_, and others _contradictory_. _Subaltern_, are universal and particular propositions of the same quality; as, _every man is a living creature_, _some man is a living creature_; or, _no man is wise_, _some man is not wise_. Of these, if the universal be true, the particular will be true also. _Contrary_, are universal propositions of different quality; as, _every man is happy_, _no man is happy_. And of these, if one be true, the other is false: also, they may both be false, as in the example given.