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. XVIII.

Of the certaintie of Mans knowledge.

WHereof dependeth the certaintie of Mans know∣ledge?

Of three things, that is, of vniuersall expe∣rience, of principles, and of naturall know∣ledge that a man hath in iudging of Conse∣quents: for these be three infallible rules of certitude or truth in all kindes of doctrine.

What is vniuersall experience?

Vniuersall experience is the common iudgement of men, in such things as are to be perceiued and knowne by the outward sences: as Fire to be hot, the Heauens to turne round about, Wine and Pepper to bee hotte in operation, Women to bring forth children, and not Men: which things all men (vnlesse they be madde, and out of their wittes) must needs confesse to be true.

What be Principles?

Principles bee certaine generall conceptions and naturall knowledges grafted in mans minde of God, to the intent that by the helpe thereof, he might inuent such Arts as are necessa∣rie in this life for mans behoofe; for by the naturall knowledge of the minde we vnderstand, Number, Order, Proportion, and all other necessarie Artes and Sciences.

How doth Aristotle define Principles?

In this manner: Principles be true Propositions, hauing credit of themselues, and need no other proofe.

How many Diuisions doe the Schoole-men make Principles?

Diuers.

Rehearse those Diuisions.

The first is, of Principles, some be called Speculatiue, and some Practiue: The speculatiue be those naturall knowledges or Propositions, whereof Naturall Philosophie or the Mathe∣maticall Sciences be grounded, as these: The whole is more then his part: Those things which are equall to a third, are

equall among themselues: of one simple body, there is but one naturall mouing, and such like. The Principles Practiue, bee those naturall knowledges, whereby mens manners are gouer∣ned: for by this naturall light we know the difference betwixt good and euill: As for example: these be Principles Practiue: God is to be honored and obeyed: Iustice is to be embraced: ciuill societie is to be maintained, and the disturbers thereof to be punished: these and such like Propositions are naturally receiued of all men as infallible verities. Againe, of Principles, some be called Generall, and some Proper. The Generall, be those that may be applied to many Sciences, as these: the whole is more then any of his parts, if equall be taken from equall, e∣quall doe remaine and such like. The proper Principles bee those, that are properly belonging to some one certaine Sci∣ence, as a line to be a length without breadth, is a principle of Geometrie: Againe, this proposition, euery thing is, or is not, is a principle of Logick: and to be short, euery Science hath his proper principles: of which some bee called dignities or Maximes, and some Positions.

Wherefore are they called Dignities or Maximes?

For that they are worthy to be credited for their selfe sake, for so soone as we heare them in such speech as we vnderstand, wee naturally know them to bee true without any further proofe, as these. Take equall from equall, and equall will re∣maine: the whole is more then any of his parts, &c.

What be Positions?

Positions be those principles, which although they need no other proofe, yet they be not so easily vnderstood of all men at the first vttering, as Maximes bee: for in these, besides the knowledge of the termes, it is needfull to haue also some ex∣perience, as in these Principles. Euery thing that is compoun∣ded of matter and forme is moueable: whatsoeuer is heauie, tendeth naturally downeward, and whatsoeuer is light, ten∣deth vpwards. Againe, of Positions, some are called Defini∣tions, and some Suppositions, and of Suppositions, some are called Petitions, called in Latine Postulata, and some Supposi∣tions assumpted.

Define these kindes.

• 1 Definition sheweth what the thing is.
• 2 Supposition is that which supposeth a thing to be, or not to be, as the Geometricians do suppose that there is Punctum, (that is to say) a pricke, or a thing indiuisible, hauing nei∣ther length, bredth, nor depth.
• 3 Petition is a Proposition asked and granted to be true: as this is a petition in Geometry, that a man may draw a right line from one point to another.
• 4 Supposition assumpted is, when a manifest supposition is assumpted to proue another thing withall, as to proue that de∣monstration consisteth of true Propositions, the disputer will assumpt this assertion, which saith, that of false things there is no certaine knowledge: and trueth is not knowne but of true things.

What is the third thing wherof the certaintie of mans knowledge dependeth?

It is the knowledge that man hath in iudging of conse∣quents, which is not altogether artificiall, but partly naturall, for God thought it not sufficient for mans behoofe to know simple Propositions, as principles or common conceptions gotten by experience, vnlesse hee could also compare them together, and ioyne things like, and agreeable together, and seuer things vnlike, and disagreeing one from ano∣ther, and by such comparison and composition to finde out things before not knowne: and to the intent wee should not erre or wander out of the right way, God hath shewed vs an order, and prescribed certain bounds and limits of necessi∣tie to be obserued in such composition, which bounds are Syl∣logismes rightly made: for so do the Consequents plainly ap∣peare: And because that proportions are knowne by nature, it shall not be amisse to giue you an example in numbers: for three knowne numbers being placed in true order of a Syllo∣gisme, a fourth number vnknowne, of necessitie doth follow, as in this question: If one pound of waxe be worth a groat, what is tenne pound of waxe worth? Marrie ten groates, which is prooued by a Syllogisme in this manner: Euery pound of

waxe is worth a groat, but here is ten pound of waxe: Ergo, they are worth ten groats: and like as in these kindes of Syl∣logismes Arithmeticall, the proportion which is to be iudged by mans naturall knowledge, doth shewe the Consequent to be infallible, euen so the Consequents in other Syllogismes are shewed to be infallible, by such demonstrations as are not farre fetched, or doubtfull, but are manifest, plaine and eui∣dent.