The arte of logick Plainely taught in the English tongue, according to the best approued authors. Very necessary for all students in any profession, how to defend any argument against all subtill sophisters, and cauelling schismatikes, and how to confute their false syllogismes, and captious arguments. By M. Blundevile.

CHAP. V.

Of conuersion of simple propositions.

WHat is conuersion?

It is the changing or turning of the subiect and predicate, the one into the others place.

How manifold is such conuersion?

It is threefold, that is, simple, by accident, and by contraposition.

What is simple conuersion?

It is that whereby the termes are onely changed the one into the others place, the selfe same quantitie and qualitie being still reserued.

What propositions are conuerted by this manner of conuersion?

An vniuersall negatiue, and particular affirmatiue.

Giue examples of both.

Of the first thus: No vertue is discommendable, Ergo no dis∣commendable thing is vertue. Of the second thus: Some man is a Philosopher, and some Philosopher is a man. And by this way sometime vniuersall affirmatiues may be also conuerted, as those whose termes are conuertible, as the speciall kinde and his diffe∣rence or propertie; as, Euery man is reasonable, and euery reaso∣nable thing is man: or, Euery man is apt to speake, and euery thing that is apt to speake, is man.

What is conuersion by accident?

It is that whereby the termes are changed, and also the quan∣titie of the propositions, but not the qualitie.

What propositions are conuerted this way?

An vniuersall affirmatiue into a particular affirmatiue, and an vniuersall negatiue into a particular negatiue.

Giue examples.

Euery patience is fortitude: Ergo some fortitude is patience. Againe: No vertue is vice: Ergo some vice is not vertue.

What is conuersion by contraposition?

It is that whereby neither quantitie nor qualitie is changed,

but only termes finite into termes infinite, that is to say, termes limited into termes vnlimited.

Which call you termes infinite?

All Nounes hauing a negatiue set before them, as, not man, not beast.

What propositions are conuerted this manner of way?

An vniuersall affirmatiue into an vniuersall affirmatiue, and a particular negatiue into a particular negatiue.

Giue examples.

Of the first thus: Euery man is a sensible body, and euery thing that is not a sensible body, is not man. Of the second thus: Some vertue is not Iustice: Ergo, some thing that is not Iustice, is not vertue. These speeches in English haue some sauour; but to be spoken in Latine, after the Schoole manner, are very barbarous, or rather monstrous, as Ualerius termeth them, as to say, Quae∣dam non Iustitia non est non virtus.