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.

Of a Syllogisme Demonstratiue.

HItherto we haue treated of a Syllogisme, accor∣ding to the first three of the foure diuisions thereof, before mentioned: for if yee remem∣ber well, we said that according to the first di∣uision, a Syllogisme is either Categoricall or Hypotheticall, according to the second diuision, eyther com∣mon or expository, according to the third diuision, eyther per∣fect or vnperfect, and according to the fourth diuision, ey∣ther Demonstratiue, Dialecticall, or Sophisticall, whereof we come now to speake, and first of a Syllogisme demonstra∣tiue.

What is a Syllogisme Demonstratiue?

A Syllogisme Demonstratiue is that which is made of ne∣cessarie, immediate, true, certaine, and infallible Propositi∣ons, being first and so knowne, as they neede none other proofe.

What meane yee by necessary and immediate Propositions?

Necessarie Propositions be those which cannot bee other∣wise, as those which doe consist of the generall kinde, of the speciall kinde, of the difference, or of the propertie, as hath beene said before: and therefore Aristotle maketh a difference betwixt a Demonstratiue and a Dialecticall Proposition, for a Demonstratiue Proposition consisting of matter naturall, is ne∣cessarily true, and cannot be otherwise, but a Dialecticall Pro∣position, consisting of matter contingent, or casuall, is onely probable, and may be otherwise.

What be immediate Propositions?

Immediate Propositions are those which are first, and haue none before them, whereby they can be proned: as euery sen∣sible bodie endued with reason is apt to learne. Aristotle al∣so setteth downe three properties or conditions belonging to the Subiect and Predicate of a Demonstratiue Proposition.

Which be those Properties?

These, to be spoken of all, by it selfe, and vniuersally.

What is to be spoken of all?

It is when the Predicate is knowne to be altogether and al∣waies in the Subiect, eyther as a part of the substance thereof, as when it is a generall kinde, the speciall kind, the difference, or the propertie, as some inseparable accident alwaies incident to the said subiect, as when I say: Euery man is a sensible bo∣die: or euery man is endued with reason: or euery man is apt to speake: or euery Swanne is white: or euery fire is hot.

What is to be spoken by it selfe?

That is, when the Predicate is eyther the definition of the Subiect, as a man is a sensible bodie endued with reason: or else some part of the Definition, as man is a sensible bodie, or man is endued with reason.

What is to be spoken vniuersally?

It is when the Predicate is in the Subiect, and in euery such Subiect by it selfe; and first, as when I say, a man is a sensible bodie endued with reason: heere this Predicate sensible bodie endued with reason, is not onely spoken of man, but of euery man in generall by it selfe: and first: for if yee should say, Pe∣ter or Socrates is a sensible bodie endued with reason: heere the Predicate is not spoken of any of these, as first, but in the second place, because they are comprehended vnder the word man. For generall kinds are said to be before speciall kindes, and special kinds before Indiuiduums, as hath bin said before.

How doth Aristotle define Demonstration?

In this sort: Demonstration is a Syllogisme made of such Propositions as are true: first immediat, and manifestly known, and be the causes of the conclusion: first and immediate here is all one, signifying such Propositions as need not to be pro∣ued or made more euident by any other former Propositions. Againe, the premises must be more knowne then the conclu∣sion, for otherwise it should neyther be Demonstration, nor yet good Syllogisme. Finally, the Premises must render the very cause of the conclusion: and therefore Aristotle in ano∣ther place saith, that Demonstration is a Syllogisme causing knowledge and science.

What is Science?

It is a firme and assured knowledge of any thing.

What is to know?

We are said to know a thing, when we know the true cau∣ses thereof, and that it cannot be otherwise: for to make a per∣fect Demonstration, we must not only shew that there is such a thing as we goe about to proue, but also we must shew the cause why it is so: for (as Aristotle saith) euery discipline and doctrine intellectiue dependeth vpon a former knowledge, which is two-fold, whereof the one is to know that the prin∣ciples (that is to say) the premises of the Demonstration bee true, and the other is to know the true signification of the Sub∣iect and Predicate of the question: for vnlesse a man know what the name of the Subiect signifieth, whereof the question riseth, and also the proper qualities of the same, how shall hee be able to iudge, whether the proofe which is brought in to proue the question withall be to the purpose or not? Againe, vnlesse he know the premises to be true, the Demonstration shall breed no certaine knowledge in him.

Giue example of a Syllogisme Demonstratiue.

Let this be your example: Euery sensible bodie endued with reason, is apt to learne: but euery man is a sensible body en∣dued with reason: Ergo, euery man is apt to learne. Heere you see that in this Syllogisme the premises being true and first, doe render the cause of the conclusion: and thereby doe imply a most true Consequent: for whoso would goe about to demonstrate any of the premises by some other former, or more knowne Propositions, should lose his labour, sith there is none before them more certaine, nor more knowne to proue this conclusion withall then they: for to vnderstand the truth of these premises, it sufficeth onely to know the signification of the termes, and to haue some experience of the thing called Man: and therefore this kinde of Demonstration is called of the Schoole-men, Syllogismus Scientificus, because it yeeldeth the perfect knowledge and Science of the thing in question.