more difficult to be retained in Memory, than a Division into more Members, all at once. For example, is it not more short and natural to say, Every Extent is either a Line, a Superficies, or a Solid, than with Ramus, Every Magnitude is a Line, or a thing Consisting of Lines; every thing consisting of Lines, is either a Superficies or a solid Body.

Lastly we may observe that it is equally erroneous not to make enough, as to make too many Divisions, the one does not sufficiently satisfy the Mind; the other confounds and amuses the Understanding. Crassotus, in great esteem among the Interpreters of Aristotle, has greatly injured his Book with a multitude of Divisions; by which we fall into that Confusion which we seek to avoid. Whatever is cut into Dust is Confused.

CHAP. XII.

Of the Definition of a Thing.

THERE are two sorts of the Definition of things, the one more exact, which retains the name of Definition; the other less exact, which is called a Description.

The more exact is that which explains the nature of the thing by essential Attributes; of which those that are common are called Genus, and those that are proper Difference.

Thus Man is defined a rational Creature. The Soul is a Substance that thinks; the Body is a Substance extended; God is a perfect Being. And great care is to be taken that the Genus in the Definition be the next, and not the remote Genus of the thing defined.

Sometimes we define by integrant parts, as when we say, a Man is defined of Soul and Body. But then there is something that supplies the place of Genus; as here the Compound Being; the rest are taken for the difference.

The less exact Definition, which is called Description, is that which gives some knowledge of a thing by the accidents that are proper to it; and so determines it, that we may frame such an Idea of it, as distinguishes from other things.

Thus we describe Plants, Fruits and Animals by their shape, by their bulk, their colour, and such like accidents. And these are the descriptions most used by Poets, and Orators.

There are also Descriptions made by the Causes, by the Matter, Form, by the End, &c. As when we define a Clock to be an Engine composed of several Wheels, whose regular motion limits the several hours.

There are three things necessary to make a Definition good? that it be universal, proper, and clear.

1. It must be universal, that is, it must contain the whole thing defined; therefore the common definition of Time, to be the measure of Motion is not good. For that is very probable that time may be the measure of Rest as well as Motion, in regard we say as well, that a thing has been so long at rest, as that it has been so long in Motion. So that time seems to be nothing else but the continuance of a thing in any condition whatever.

2. It must be proper, that is, it must agree with the thing defined. Therefore the common Definition of Elements, to be a Simple Corruptible Body, is erroneous. For the Heavenly Bodies being no less simple Bodies than the Elements by the Confession of the Philosophers, we have no reason to believe but that there are alterations in the Heavens analogous to those that happen upon Earth; since not to speak of Comets, which we now find are not formed of the Exhalations of the Earth, as Aristotle imagined, we discover spots in the Sun, which gather together, and then scatter again in the same manner as our Clouds, though much larger in extent.

3. It must be clearer; that is, it ought to render the Idea of a thing defined, more plain and distinct, and make us as much as may be to understand the nature of it, and be serviceable to us to give a reason of its principal Properties. Which is that which we ought principally to consider in Definitions, and which is wanting in the greatest part of Aristotle's.

For whoever understood the nature of motion, the better for the help of this Definition; An Act of Ens in Potentia, as in Potentia, or Power? Is not the Idea of it, wherewith Nature furnishes us, a hundred times more clear than that? and indeed what did it ever avail to explain the Properties of Motion?

The four celebrated Definitions of the four first qualities are nothing better.

Dry, says he, is that which is easily retained within its bounds, and difficultly within those of another Body.

Moisture, on the other side is that which is easily retained in the Bounds of another Body, difficultly within its own.

These Definitions better agree with hard and Liquid Bodies, than with Bodies moist and dry. For we say of the Air, that here it is dry, in another place moist, though it be always easily retained with the Bounds of another Body, as being always Liquid. Moreover we do not see how Aristotle could say that Fire, that is, Flame, was dry according to this Definition, because it is easily confined within the Bounds of another Body. Whence Virgil

calls it liquid Fire. And it is a vain subtilty to say with Campanella, that Fire enclosed, either breaks or is broken; for that proceeds not from its pretended dryness, but because its own Smoke stifles it, if it have not Air, and therefore it will be more easily restrained within the limits of another Body, provided it may have some Breathing-hole to let out the Smoke which it continually sends forth.

As for hot, he defines it, that which congregates Homogeneals, and separates Heterogeneals.

Cold he defines that which unites Heterogeneals, and dissipates Homogeneals. Which sometimes agrees as well with Hot as with Cold; but not always, and which is of no use, neither to shew us the cause why we call some Bodies Hot, and others Cold. So that Chancellor Bacon had reason to say, that these definitions were like those that should define a Man to be a Shoemaker, or a Vine-dresser.

The same Philosopher defines Nature, the Principle of Motion and Rest, in that wherein it is. Which is grounded upon an opinion that he had, that all natural Bodies differed in this from Artificial Bodies, that natural Bodies, had in themselves the Principle of their Motion, and that the motion of Artificial Bodies was from without; whereas it is evident that no Body can give motion to itself: in regard that matter being indifferent either to Motion or Rest, cannot be determined to either of these, but by an extrinsic cause, which not being able to proceed to Infinity, it follows that God alone gives motion to matter, and preserves it in its Motion.

His celebrated definition of the Soul is no les defective. The first act of a natural organic Body, that has life in Power.

First it does not appear what he would define. For if it be the Soul, as common to Man and Beast, it is a Chimera which he has defined, there being nothing common between those two things.

2. He has explained an obscure Term by four or five that are more obscure. For to omit the rest, the Idea which we have of the word Life, is no less confused than that which we have of the Soul; these two Terms being equally ambiguous and equivocal.

These are the Rules of Definition and Division; but though there be nothing of more moment in the Sciences than to define and divide well, we need say no more in this place; because it depends much more upon the knowledge of the Subject in dispute, than upon Logical Rules.

CHAP. XIII.

Of the Conversion of Propositions, where is a thorough Inquisition into the Nature of Affirmation and Negation, upon which this Conversion depends. And first of the Nature of Affirmation. I HAVE deferred till now to speak of the Conversion of Propositions, because upon that depends the Foundation of all Argumentation, of which we are to discourse in the next part. And therefore it was not proper that this matter should be remote from what we have to say of the nature of Arguments, though it behoves us to repeat some thing of what we have said concerning Affirmation and Negation, that we may thoroughly explain the Nature both of the one and the other.

Certain it is, that we cannot explain a Proposition to others, but we must make use of two Ideas, the one for the Subject, the other for the Attribute; as also of another word which denotes the Union, which our understanding conceives between them.

This Union cannot be better expressed than by the words themselves which we make use of to affirm, while we say, that one thing is another thing.

From whence it is evident, that the Nature of Affirmation is to Unite and Identify, as I may so say, the Subject with the Attribute; for this is that which is signified by the word est, it is.

And it follows also, that it is the nature of Affirmation to apply the Attribute to all the Individuals that are expressed in the Subject, according to the Extent which it has in the Proposition, As when I say, Every Man is a Creature, I would signify, that whatever is Man is also a Creature; and so I conceive a Creature to be in all Men.

Whereas if I only say, some Man is just, I do not unite the Attribute of Just to all, but only to some one Man.

Here we must also consider what has been already said, that in Ideas we must distinguish their Comprehension from their Extension; for that the Comprehension marks out the Attributes contained in one Idea; and the Extension the Subjects which contain that Idea,

For thence it follows, that an Idea is always affirmed according to its Comprehension, for that by depriving it of some one of its Essential Attributes, it is entirely annihilated, so that it is no more the same Idea. And by consequence when it is affirmed, it is always according to all that which it comprehends in itself. Thus when I say, that a Rectangle is a Parallellogram, I affirm of a Rectangle all that is comprehended in the Idea of a Parallel

logram. For if there were any part of this Idea, which did not agree with a Rectangle, it would follow, that the Idea itself did not agree with it, but only one part. And therefore the word Parallellogram ought to be denied, and not affirmed of a Rectangle. Which we shall find to be the Ground of all Affirmative Arguments.

And it follows, on the other side, that the Idea of the Attribute is not taken according to its full Extension; at least that its Extension was not greater than that of the Subject.

For if I say, that all Lascivious Men are damned, I do not say they only shall be damned, but that they shall be of the number of the damned.

Thus the Affirmation placing the Idea of the Predicate in the Subject, it is properly the Subject which determines the extension of the Attribute, in an Affirmative Proposition, and the Identity which it denotes, regards the Attribute, as included in an extent equal to that of the Subject; and not in all its Universality, if it have any more than the Subject. For it is true, that Lions are all included in the Idea of Creature, but it is not true that they are all the Creatures that are.

I have said, that the Predicate is not taken in its full Generality, if it have any more than the Subject. For not being restrained but by the Subject, if the Subject be as general as the Attribute, it is clear, that the Predicate shall enjoy all its Generality, because it shall have as much as the Subject, and for that we suppose, that according to its own nature it cannot have more.

From whence we may gather these three undoubted Axioms,

1. AXIOM.

The Attribute is placed in the Subject by the Proposition affirmative, according to the full extent of the Subject in the Proposition. That is, if the Subject be Universal, the Attribute is conceived in the full extent of the Subject; and if the Subject be particular, the Predicate is only Conceived in a part of the Extension of the Subject: As in the foregoing Examples.

2. AXIOM.

The Predicate of an Affirmative Proposition, is affirmed according to its full Comprehension: That is to say, according to all its Predicates.

3. AXIOM.

The Predicate of an Affirmative Proposition, may be affirmed according to its full Extension, if it be in itself greater than that