An entire body of philosophy according to the principles of the famous Renate Des Cartes in three books, (I) the institution ... (II) the history of nature ... (III) a dissertation of the want of sense and knowledge in brute animals ... / written originally in Latin by the learned Anthony Le Grand ; now carefully translated from the last corrections, alterations, and large additions of the author, never yet published ... by Richard Blome.

CHAP. XXII. Of the Method of Composition.

I. What use we are to make of the Synthe∣tical Me∣thod. THis Method is called the Method of COM∣POSING, because it makes use of Ge∣neral and Common things, to come to things Par∣ticular and Compound: As for Example, If I have a mind to teach another by the way of Synthe∣tical Method, that the Soul of Man is Immortal, I begin with these general Maxims; That Every Being is either a Substance, or a Mode; that there are two Substances, viz. a Thinking Substance, and an Extended Substance; that no Substance can properly be said to perish; that what we call Destruction in a Bodily Substance, is only a Disso∣lution of its Parts: Whence I conclude, that that which hath no Parts, as the Soul, cannot be de∣stroyed, and that by consequence it is Immortal.

II. Why Syn∣thetical Method proceeds from things General, to less Gene∣ral. I have said, that the Method of Compounding proceeds from more Universal things, to such as are less Universal; and it does so, because by this way of proceeding, all Repetitions, which com∣monly occasion Confusion and Tediousness, may be avoided. For should we treat of Species, before we have spoken of the Genus; forasmuch as we cannot know the Species, without knowing the Genus first, we should be fain to explain the Na∣ture of the Genus, as often as we had occasion to treat of any Species. But because this way of De∣monstration is peculiar to Geometricians, and is look'd upon by them as very necessary to persuade Truth, we will borrow from them whatsoever we

have to say concerning it, to the end that we may follow the same way in searching out the Know∣ledge of other things, which they use in the de∣monstration of Matters Geometrical.

III. What things Ma∣thematici∣ans make use of in their De∣monstra∣tions. Mathematicians are wont to deduce those things that are of the greatest moment and weight from known and easie Principles, by a Chain of Simple Truths; which they refer to three kinds; the first whereof includes Definitions: As, a Right Line is that which is the shortest betwixt two Points. A Point is that which hath no Parts. The second contains Postulata, or things demanded or taken for granted, which are so evident as to need no confir∣mation, and want nothing but the Hearers assent, viz. that from any Center, and at any distance, a Circle may be described. The Third comprehends Axioms, or common Notions of the Mind, which are not only manifest and evident in the Science we are treating of, but also in all others: As that all Right Angles are equal amongst themselves; that which is Equal, is bigger than all its Parts taken together.

IV. Three things are required to the Ex∣torting an Assent. Hence three things are chiefly observed by Geo∣metricians, for the forcing of Assent. First, That no Ambiguity be left in the Terms, which is easily avoided by the Definitions of the Terms, which (as was said before) are nothing else but open Expli∣cations of the Terms and Words by which the things under debate are signified. The Second is, That every Ratiocination be founded on clear and distinct Principles, being so evident, that whosoever rightly understands the Words, must needs give his Assent to them. Which is the Reason why Ma∣thematicians do always presuppose their Axioms, which they require to be granted them, as being so evident, that they stand in need of no Explication. The Third is, That every Conclusion they propound be proved demonstratively, making use only of those Definitions they have already alledged, or such Principles as have been granted them: Or lastly, Propositions, which by force of Argument they have deduced from them. So that all which Ma∣thematicians observe concerning this matter, may be reduced to these Heads, which we shall compre∣hend in the following Rules.

Rules of Definitions.

V. First Rule of Defini∣tions. The First, That every Obscure or Equivocal Term be defined.

VI. Second Rule. The Second, That no Terms do enter the Defi∣nition, which are not altogether clear, or have not been before explained.

Which two Rules are of that necessity, that they cannot sufficiently be imprinted in our Minds; forasmuch as by this means many Disputations are taken out of the way, which oft consists only in the Ambiguity of Words; as when the same Term is by divers Persons taken in a different Sense; which is a thing that happens very frequently in Schools. Wherefore, for the Removal of so many Disputations, which often do arise amongst the divers Sects of Philosophers, it will be sufficient if the Disputing Parties take care to explain distinctly, and in few words, what they conceive by the Term about which they Dispute, and what they would have others to understand by it. As for the Qualifications of the Definitions of things, of these we have treated in the Fourteenth Chapter.

The Rule of Axioms.

VII. A Rule for Axioms. This is a Rule of Axioms, That no Propositions be set up for Axioms, but such as are most manifest and evident.

For no body questions, but that there are some Common Notions of the Mind that are so clear and perspicuous, as to stand in need of no Demonstra∣tion, to make them appear more distinctly. For did they involve the least Doubtfulness, they could not be the Foundation of a certain Conclusion. And therefore they are called Axioms, or common E∣nunciations, because they are so clear and manifest, as to stand in need of no Demonstration.

VIII. The Evi∣dence of Axioms doth not arise from the Senses. But we are not to suppose, as some do, that the Certainty and Evidence of Propositions doth in any degree proceed from the Senses; for that is abso∣lutely false. For the Truth-discerning-Faculty is not placed in the Senses, which are often deceived by a Similitude of Things, and are not able to dive into the Difference that lies hid in them. Who is it that doth not experience how narrow and weak our Senses are, and how frequently they deceive us, when we go about to search out any thing by their means?

For altho' this Axiom, That the Whole is greater than any one of its Parts, be in some sort discer∣nible by the Senses, yet not with such a Certainty as is necessary to Science; because whatsoever our Senses discover to us concerning it, is only founded on the observations of ou•• Infancy, which cannot afford us an undoubted, but only a probable Cer∣tainty. For by Induction a thing cannot be cer∣tainly known, except we be certain of the fulness of the Induction; there being nothing move com∣mon, than for us to discern at last the falsity of those things, which from general Inductions we were persuaded to be most True. The whole Truth of this Proposition, the Whole is bigger than its Parts, doth depend on the clear and distinct Notions we have of the Whole and Parts, by which we judge that the Whole is greater than any one of its Parts, and that the Part is less than the Whole. For when we are discoursing of any thing that is firm and stable, we must not have recourse to the Senses, as Plato saith; but to constant, im∣mutable, and impregnable Reasons. Thus we clearly know, that a Triangle is a Figure, that the Number Two is an even Number; because the Notion of a Figure is contained in the Definition of a Tri∣angle; and in that of the Number Two, the Notion of an Even Number.

IX. The Cer∣tainty of Propositions depends on the clear Knowledge we have of them. Wherefore all the Certainty of our Knowledge in Natural things, depends on this Principle, Whatsoever is included in the clear and distinct Idea of any thing, the same may with truth be affirmed of it. Thus because Substance is included in the Conception of a Body, we may affirm a Body to be a Substance. Because it is involved in the Idea of a Circle, to have equal Diameters, we may assert of every Circle, That all their Diameters are Equal. Because it is included in the Idea of a Triangle, that all its Angles are Equal to two Right ones, we may affirm the same of all Tri∣angles. What must be the Qualifications of Axioms, appears from what we have said of the framing of Propositions that are necessarily true, in the Thirteenth Chapter.

Most General Axioms.

X. To have many Axioms in a readiness, is a great help to ready Ar∣guing or Ratiocina∣tion. But forasmuch as it is of great use, to have good store of Axioms at hand, whereby to prove and discover what is obscure and abstruse; it will be ne∣cessary to set down here some general and neces∣sary Propositions, from which as so many Foun∣tains, more special ones as Rivulets may be de∣rived.

I. Whatsoever is comprehended in the clear and distinct Conception of any thing, the same may with Truth be affirmed of it.

For since in the clear and distinct Conception of a Body Extension is contained, and Cogitation in the Idea of the Soul, I can truly affirm of a Body that it is extended; and of the Soul, that it is a Thinking Substance. Wherefore we are to lay down this, as the Foundation of all Sciences; that we must never give our full assent to any Proposi∣tion, which doth not appear evidently true to us, so as that we cannot but assent to it, without doing violence to our Minds.

II. In every Idea or Conception is involved either Possible or necessary Existence.

Since nothing can be apprehended by us, except under the notion of being Existent; that is, neces∣sary Existence is comprehended in the notion of a Being absolutely perfect, that is, of God; and pos∣sible Existence in that of a Creature, or of a limi∣ted and finite Being.

III. Nothing has no Affections or Properties.

So it cannot be said, that nothing is Divisible, that it hath Parts, that it can be moved, &c. Wherefore, wheresoever any Property is found, there we may assert that there is a True and Real Being.

IV. Nothing cannot be the Cause of any Thing.

Forasmuch as the Cause of a Thing is supposed to be, before it can produce any thing, and that Nothing cannot exist, it doth follow, that neither can it be Principle or cause of any thing. For if Nothing could ever be Something, it would follow, in opposition to the foregoing Maxim, that it must have some Property, which is a Contradi∣ction.

From this Axiom, some others are deduced by way of Corollaries; such as are,

V. Nothing, nor any Perfection of a thing, actu∣ally Existent, can have Nothing, or a thing not Existing, for the cause of its Existence.

Another Corollary:

VI. Whatsoever Reality, or Perfection there is in any thing, the same is formally, or eminently in the first, and adequate cause of that thing.

Whence it follows, that the Objective Reality of our Idea's, requires a Cause in which the same Re∣ality, is contained, not only Objectively, but For∣mally, or Eminently. For this Axiom doth not only belong to the Efficient Cause, but also to the Exemplary. For if an Image be made more excel∣lent than its Exemplar or Original, so that more Perfections are found in it, than in the thing it self, after the likeness of which it is made, it cannot be said to imitate its Exemplar, and consequently can∣not properly be called its Image.

VII. A Thing or Substance, cannot naturally be Annihilated.

That is, it cannot so cease to be, as that nothing at all should remain of it. For we easily conceive, that when any thing ceaseth to appear, it doth chage its Nature, or is converted into another thing; As for Example, we can well enough conceive, how Wood comes to cease to be Wood, how it comes to be Fire, and how the several Particles of Fire are subdivided into others, that at last they cannot be perceived by any Sense: But we can by no means conceive, how they should be reduced naturally to nothing, and from Being pass, to not Being.

VIII. That which is clear and evident is not to be denied, because that which is obscure, cannot be comprehended.

For we cannot doubt, but that there is Liberty and Indifferency in us, because we are conscious of it, and comprehend nothing more evidently or per∣fectly, tho' we cannot comprehend, how God doth leave the free actions of Men indetermined.

IX. It is the nature of a Finite Mind, to be un∣able to comprehend that which is infinite.

Because it is the nature of an Infinite being, to be Incomprehensible; for if it could be compre∣hended, it would not be Infinite. What wonder is it therefore, that we cannot conceive matter to be Divisible into Infinite? Or that we cannot under∣stand the Mystery of the Trinity, or the Incarna∣tion of the Divine Word? Because our Mind is Finite, and bears no propotion to the Mysteries. Would but some Men weigh this Axiom, as they ought, they would not with so much obstinacy, rely upon their weak Reason, or trusting to their own Wits, invent a new kind of Divinity.

X. If you take Equals from Equals, what re∣mains will be Equal.

XI. If you add Equals to Equals, the whole will be Equal.

XII. It is in vain to endeavour that by more, which can commodiously be performed by less.

Special Logical Axioms.

Logical Axioms are of great use. To these we may subjoyn some Logical Axi∣oms, which are of great use, in the guiding of our Discourse, and are taken from the Genus, Species, Difference, Division, Causes, &c.

From the Genus.

I. Whatsoever is affirmed or denied of the Genus' the same is affirmed or denied of the Species.

The reason is, because the Genus contains the Species, and because the whole Essence of the Genus is found in them: Thus, because it is affirmed of an Animal, that it is Sensitive, the same is also affirmed of Man and Beast. And because the same Animal is denied to be a Stone, so likewise, the same is denied of a Man and a Beast. Where∣fore, the Genus is of no use to prove the Species, but only to remove it. For that which is not an Animal, neither can it be a Man; but that which is a Man, must therefore be an Animal.

II. The supposing of the Genus, doth not suppose such a Species.

As for Example, supposing any thing to be an Animal, it cannot from thence be concluded, that it is a Man; because it may be a Beast, which is likewise an Animal.

II. The Genus being destroyed, the Species must be destroyed with it.

For seeing that the Genus is an essential part of the Species, it must follow that the Genus being destroyed, that must needs be destroyed with it, which consists of it. Thus if we take away an

Animal, we together take away the Species, that are contained under it. And by taking away a Foursquare Figure, we at the same time take away a Parallelogram and a Trapezium, which are the Species of a Foursquare.

From the Species.

I. The supposing of the Species, supposeth the Genus; but the taking away of one Species, doth not necessarily remove the Genus.

Because the Idea of the Genus, is comprehend∣ed in the Essential Conception of the Species, with∣out which the nature of the Species cannot be ex∣plained. So supposing a Binary or the number two, we suppose a number also; and asserting a Parallelogram, we likewise assert a Square. And if all Beasts were taken out the World, yet would not Animal be therefore taken away, seeing it would be preserved in Man. Hence it is, that the Species is of great force to prove the Genus, but of none at all to deny it. For that which is a Binary, must be a number, but it does not follow, that that which is no Binary, is therefore no number.

II. All the Species being destroyed, the Genus is destroyed likewise.

For in this case all the power of the Genus is ex∣hausted, neither doth there any thing remain, of which it can be affirmed. So supposing the Sight, Hearing, Tasting, Smelling and Feeling to be de∣stroyed; the outward Sense must be destroyed like∣wise: And taking away Prudence, Justice, Tem∣perance and Fortitude, takes away Vertue also.

From the Form or Difference.

I. The Form is that by which a thing is, what it is.

Because the Form or Difference, is the chief Es∣sential Attribute that is found in the Species, and whose property it is to constitute the same, and distinguish it from other Species. Thus Extension constitutes a Body, and Cogitation the Mind or Soul of Man.

II. Where the total Difference or Form can be affirmed or denied, of the same the Species also may be affirmed or denied.

This Axiom as a Corollary is deduced from the former; for seeing the thing is constituted by the difference, where the same is found, it is necessary that there the Species be also. Thus, because Cogi∣tation may be affirmed of the Mind of Man, there∣fore we may affirm it to be a Thinking Being.

III. The Form and Species are reciprocated.

The Reason is, because Difference constitutes the Species, and doth distinguish it from other Species, and therefore must have the same latitude as the Species it self, and therefore must reciprocally be affirmed of one another: As, Every thing that Thinks is a Mind, and every thing that is a Mind Thinks.

From the Property.

I. The Property is consequent on the Form.

For the Property is something flowing from the nature of the Species, and so bound to it, that it agrees to the whole Species: So Divisibility follows Extension, and is so necessarily joyned to it, that no Body can be extended, but that it must be Divisi∣ble also.

II. The supposing of the Form, supposeth the Proper∣ty, and the taking away of it, takes away the Property also.

As when Extension is supposed, Impenetrability and Divisibility are supposed likewise; and if that be taken away, the Properties are taken away also.

From the Definition.

I. Whatsoever agrees with the Definition, agrees also with the thing Defined.

For seeing that a Definition declares the nature of a thing, by its Essential Attributes, viz. by its Genus and Difference, it must include the Whole, contained in the thing defined; and there∣fore whatsoever is Attributed to the Definition, the same must necessarily be also Attributed to the thing defined. Thus, because it agrees to the Art of Discoursing well, to direct the Mind; there∣fore also it must agree to Logick, to direct the Mind.

II. If the Definition belong to a thing, the thing defined must also belong to it.

Thus, because it belongs to the Mind of Man, to be a Thinking Substance, it belongs also to the same to be a Spirit. And because to a Stone, belongs Extension in Length, Breadth and Depth, therefore it also belongs to it, to be a Body.

III. If a Definition agree with a Definition, the thing Defined also, must agree with the thing Defined.

As, That which consists of a Body and Mind, is endowed with Sense; therefore Man is an Ani∣mal. Substance is something which hath an Es∣sence and Existence distinguisht from all other things; and on the contrary.

From Division.

I. If no part of the Division agrees to a thing, neither doth the thing divided agree with it.

Thus, because the notion neither of a Spirit nor Body, doth agree to Substantial Forms (save only the Soul of Man.) Therefore, Substantial Forms cannot be Substances.

II. Every Division must be entire, that is, it Enumerates all and every Part belonging to a thing.

For should any part belonging to a thing, be omitted in the Division, there could not be an Adequate Enumeration of the Parts, neither con∣sequently would the thing, by means of such a Division, be distinctly perceived. Thus the Di∣vision of a Man into Sound and Sick, is not Ade∣quate, because there is a kind of Middle State, as, is that of a Man, that is recovering from Sickness. But the Division of Hand into Right and Left; of a Line into Right and Crooked; of a Number into Even and Odd, is Adequate because it Enu∣merates all and every Part.

III. The Parts of a Division must be opposit.

This Axiom follows from the foregoing. Thus things are better divided into Material and Immate∣rial, than into Visible and Invisible; because some Invisible things, as a very clear Air, and our Breath, are not by nature distinct from Visibles.

From the Cause.

I. The Cause is always before the Effects

For seeing the Cause is that from which a thing hath its Original, or that of which that Being doth in some sort depend, therefore it must needs exist before it. So a Carpenter is before the Building; A Father before the Son, &c. A Cause is in a twofold Sense said to be before its Effect, viz. by a Priority of Nature and Time. A Cause is before

its Effect by a Priority of Nature; because the Effect exists by the Power of the Cause, and not the Cause by the power and virtue of the Effect; yet not always by priority of Time, because some Effects exist at the same time with their Causes, as all those Effects which proceed by Emanation; as the Proprieties do from their Subjects, which therefore exist the same moment with them.

II. Nothing can be a Cause of it self.

For seeing there is a Dependance in the Effect, whereby it proceeds from something that was be∣fore it; it cannot be conceived, how any thing should be prior to it self.

III. Supposing the Cause in Act, we suppose the Effect in Act also.

The Reason is, because when the Cause is con∣stituted in Act, it always does something, and that which it does is called its Effect. As supposing God a Producer, we must necessarily suppose some∣thing produced; and therefore the Cause and its Effect, as well as other Relates, are said to be simul Natura, that is, to be both at once; for no sooner is one Relative named, but at the same time we understand the other. So he is a Father, who hath a Son; and he a Son, who hath a Father.

IV. A Cause cannot give that which it hath not.

For a Cause gives something to another thing, but it cannot give that which it self wants.

V. Whosoever Acts by another, is esteemed to act of himself.

As he who desires, exhorts, and adviseth others to commit some Wickedness, is said to be the Moral Cause; because by Desiring or Commanding, &c. He makes the Effect to be imputed to him.

From the Effect.

I. The Effect is posterior to its Cause.

This Axiom follows from the foregoing: For if the Cause be before the Effect, it follows that the Effect must presuppose it.

II. No Effect exceeds the virtue of its Cause.

For seeing the Effect borrows its Being from the Cause, it is impossible it should take any thing that goes beyond or exceeds the Power of its Cause. For Fire would never be able to warm the Hand, if to warm did exceed the virtue of Fire.

III. That because of which every thing is such, is it self more such.

That is, if the Nature of the Effect be good or bad; the same doth more clearly appear in the Cause. This is true when both are capable of the same Quality: Thus because the Kettle is hot be∣cause of the Fire, the Fire must needs be more hot. But we cannot argue, a Man is satiated with the Meat he eats, therefore the Meat is more satiated.

From the Subjects, and Adjuncts.

I. Where the Subject is, there are the Adjuncts also.

For seeing that the Adjunct is the Mode of the Subject, it does always accompany the fame: As where the Fire is, there is heat; where a Dead Carkass is, there is a stink.

II. Such as the Subject is, such are the Ad∣juncts.

For such as the Orator is, such is his power in Persuading; as the Sick is, such are his symptoms.

III. Where the Adjuncts are, there is the Sub∣ject.

Because Adjuncts are added to the Subject, and are considered as things that belong to it. As where Motion, Magnitude, &c. is found, there must also be a Body.

From the Whole.

I. What agrees to a Similar Whole, agrees also to the Parts of it.

For seeing that a Similar Whole is made up of a Conjunction of Similar Parts, it must needs be of the same Nature with them. Thus, because Lead is heavier than Brass; therefore every part of Lead, proportion being observed, must be heavier than Brass.

II. Where any Whole is, there are all its Prin∣cipal Parts.

For the Principal Parts are Essential to the Whole. I say, the Principal Parts, as the Head, and the like; because there are some Parts which belong to the Entireness, but not to the Essence of the thing.

III. The Entire Whole being supposed, all its Parts are supposed also.

The Reason is, because this Whole is nothing else than the Parts taken all together: As where the Entire Body of Man is, there must be its Skin, Bones, Sinews, Veins, Flesh, and all things that belong to the Entireness of it.

From the Parts.

I. Every Part, with respect to its Whole, is Imperfect, and Incompleat.

So the Soul and Body, with respect to a Man, are Imperfect and Incompleat; because they both belong to make a Perfect Man. So the Hands, Feet, Head, which are the Integral Parts of Mans Body, are more Imperfect than the Whole Body.

II. Where all the Parts are, and joyned together, there is the Whole.

This Axiom is evident from what hath been already said.

From Like and Ʋnlike.

I. Like do agree with Like.

A Prince must govern a Commonwealth after the same manner, as a Father of a Family takes care of his Family.

II. To Unlike things, Opposits do agree.

As we love an Honest man, so we hate a Wicked person. A Shepherd feeds his Sheep, an Hireling neglects them.

From Relates.

I. Relates are by Nature together, or at one and the same time.

For seeing that every Relation is mutual, and one Relative respects the other; it cannot be, but that if you put the Relate, you must put the Correlate likewise: And therefore the Cause and the Effect, that which is before, and that which is after, and all other things that do mutually respect each other, are always at once and together in the Mind. From whence follows also this Axiom.

II. One Relative being put, the other is put also; and being taken away, the other is so likewise.

From Contraries.

I. That which is susceptive of one Contrary, is also susceptive of the other.

As Water can be made hot, therefore it may also be made cold. A Dog cannot act justly, and there∣fore neither unjustly.

II. Of Contraries, it is necessary that the one be in the Subject susceptive of it; the other not.

Thus if a Number be not Even, it must be Un∣even. Yet this Axiom doth not hold in all Con∣traries; for it is not necessary that a Wall should be white, because it is not black.

From Privative Opposits.

I. If the one be Absent, the other must be absent also.

This must be understood in a Capable Subject. As if a Man sees, he is not blind. It is Light, therefore not Dark.

II. For the Most part, there is no going back from a Privation to a Habit.

As from Death to Life, from Blindness to Sight.

III. What in one Subject is Privation, is often a Negation with regard to another.

This appears in our Errors, which with refe∣rence to God, who doth not bestow upon us the whole knowledge of Truth, are only called Ne∣gations; but with reference to us are Defects and Privations. Thus Ignorance of the Laws is blame-worthy in him, who professeth skill in Law; but not to him who is of another Profession.

From Contradictories.

I. One Contradictory being put, the other is re∣moved; and on the contrary.

As supposing that Peter walks, it cannot be that he should not walk.

From Parity, or Equality.

I. Even things with Even things agree, or dis∣agree.

As Faith to the Patriarchs was necessary to Salvation; therefore to us also.

From the Greater.

I. If that which is more Likely is not; much less that which is less Likely.

As if a Woman could not be tempted to Sin by an hundred Guinea's, much less by thirty.

From the Lesser.

I. If that which is less Likely is, much more that which is more likely.

As, a Man hath kill'd the King, therefore he will make no difficulty of killing one of his Fellow-Citizens.

From Divine Authority.

I. The Testimony of a Being Sovereignly In∣telligent, Wise, and True, is of greater efficacy to persuade, than any other the most strong and evi∣dent Reasons that may be.

Thus since God tells us, that they are blessed who are persecuted for Righteousness sake, we are to hold it for an undoubted Truth; because we have a greater Certainty, that he who is Sove∣reignly Intelligent, and Infinitely Good, cannot be deceived, than we can be certain that we our selves are not deceived, even in those things that appear most clear and evident to us. For we are to give credit to the Divine Testimony, not be∣cause of the Affirmation or Negation, but for the Authority of the VVitness, as being Omnipotent, Omniscient, and of the most Sovereign Veracity and Truth.

From Human Authority.

I. VVe ought not to oppose that which is owned by all Men, or most Men, or wise Men, or by the most Famous and most Approved of them.

As for Example, it is a Truth received by the common censent of all Men; that we ought to venture our Lives for the welfare and safety of our Native Country: And that it is the Duty of every Man, to live honestly, to hurt no body, and to give to every Man his Right. For this unanimous Agreement of all Men shews, that their Judg∣ment in these Cases proceeds from common inborn Notions, and not from any Compact to impose upon others, or deceive themselves.

But yet we must not have the same Opinion of those Men, who being over-credulous, deceive others, by reporting Prodigies which they had from others; as that there are Sciopodes, Men that have but one Foot, and that so great, that lying on their Backs they can shade their whole Body with it; or that there are Men that have so great Ears, that they reach down to their Feet, and so broad that they can lye upon them; and others again that have no Heads, and have their Eyes about their Shoulders: Because we are not to believe every one, but only those whose sufficient know∣ledge of the Matters they relate, and Veracity, are fully known to us.

Two Rules of Demonstrations.

I. All Propositions that involve any thing of Obscurity, are to be proved without alledging any thing in proof of them, besides Definitions which have gone before, or Axioms that have already been granted, or Propositions before demonstrated, or the Construction of the thing in discourse, when any Operation is to be done.

II. VVe are never to make an ill use of the Equivocation of Terms. This may be occasioned by not adding their Definitions, to restrain or ex∣plain them. For to every true Demonstration two things especially are required. First, That in the Matter it self nothing be contained, but what is certain and indubitable: The Other, That there be no fault in the Form of Argumentation: Which Faults we shall avoid by the Rules now given, that is, by not making an ill use of Equivocal Terms, and by using no other Propositions in our Demon∣strations, but what are either Definitions of Terms before explained, or Axioms that have been before granted, and which ought not to have been sup∣posed, without being sure of their Evidence; or Propositions, that have been before demonstrated, or the Construction of the Thing of which we treat, when any operation is to be performed. For by observing of these things all Defects or Mistakes will be easily avoided both in Matter and Form.

As to the Constitution of Demonstrations, we have handled it in the Nineteenth Chapter of the Third Part.