The Ethics by Benedictus de Spinoza (most important books of all time .txt) 📖

movements should preserve among themselves a certain

fixed relation, we say that such bodies are in union, and that

together they compose one body or individual, which is

distinguished from other bodies by the fact of this union.

Axiom III.-In proportion as the parts of an individual, or a

compound body, are in contact over a greater or less superficies,

they will with greater or less difficulty admit of being moved

from their position ; consequently the individual will, with

greater or less difficulty, be brought to assume another form.

Those bodies, whose parts are in contact over large superficies,

are called hard ; those, whose parts are in contact over small

superficies, are called soft ; those, whose parts are in motion

among one another, are called fluid.

LEMMA IV. If from a body or individual, compounded of

several bodies, certain bodies be separated, and if, at the same

time, an equal number of other bodies of the same nature take

their place, the individual will preserve its nature as before,

without any change in its actuality (forma).

Proof.-Bodies (Lemma i.) are not distinguished in respect of

substance : that which constitutes the actuality (formam) of an

individual consists (by the last Def.) in a union of bodies ; but

this union, although there is a continual change of bodies, will

(by our hypothesis) be maintained ; the individual, therefore,

will retain its nature as before, both in respect of substance

and in respect of mode. Q.E.D.

LEMMA V. If the parts composing an individual become greater

or less, but in such proportion, that they all preserve the same

mutual relations of motion and rest, the individual will still

preserve its original nature, and its actuality will not be

changed.

Proof.-The same as for the last Lemma.

LEMMA VI. If certain bodies composing an individual be

compelled to change the motion, which they have in one direction,

for motion in another direction, but in such a manner, that they

be able to continue their motions and their mutual communication

in the same relations as before, the individual will retain its

own nature without any change of its actuality.

Proof.-This proposition is self-evident, for the individual

is supposed to retain all that, which, in its definition, we

spoke of as its actual being.

LEMMA VII. Furthermore, the individual thus composed

preserves its nature, whether it be, as a whole, in motion or at

rest, whether it be moved in this or that direction ; so long as

each part retains its motion, and preserves its communication

with other parts as before.

Proof.-This proposition is evident from the definition of an

individual prefixed to Lemma iv.

Note.-We thus see, how a composite individual may be affected

in many different ways, and preserve its nature notwithstanding.

Thus far we have conceived an individual as composed of bodies

only distinguished one from the other in respect of motion and

rest, speed and slowness ; that is, of bodies of the most simple

character. If, however, we now conceive another individual

composed of several individuals of diverse natures, we shall find

that the number of ways in which it can be affected, without

losing its nature, will be greatly multiplied. Each of its parts

would consist of several bodies, and therefore (by Lemma vi.)

each part would admit, without change to its nature, of quicker

or slower motion, and would consequently be able to transmit its

motions more quickly or more slowly to the remaining parts. If

we further conceive a third kind of individuals composed of

individuals of this second kind, we shall find that they may be

affected in a still greater number of ways without changing their

actuality. We may easily proceed thus to infinity, and conceive

the whole of nature as one individual, whose parts, that is, all

bodies, vary in infinite ways, without any change in the

individual as a whole. I should feel bound to explain and

demonstrate this point at more length, if I were writing a

special treatise on body. But I have already said that such is

not my object ; I have only touched on the question, because it

enables me to prove easily that which I have in view.

POSTULATES

I. The human body is composed of a number of individual

parts, of diverse nature, each one of which is in itself

extremely complex.

II. Of the individual parts composing the human body some

are fluid, some soft, some hard.

III. The individual parts composing the human body, and

consequently the human body itself, are affected in a variety of

ways by external bodies.

IV. The human body stands in need for its preservation of a

number of other bodies, by which it is continually, so to speak,

regenerated.

V. When the fluid part of the human body is determined by an

external body to impinge often on another soft part, it changes

the surface of the latter, and, as it were, leaves the impression

thereupon of the external body which impels it.

VI. The human body can move external bodies, and arrange

them in a variety of ways.

 

PROP. XIV. The human mind is capable of perceiving a great

number of things, and is so in proportion as its body is capable

of receiving a great number of impressions.

Proof.-The human body (by Post. iii. and vi.) is affected in

very many ways by external bodies, and is capable in very many

ways of affecting external bodies. But (II. xii.) the human

mind must perceive all that takes place in the human body ; the

human mind is, therefore, capable of perceiving a great number of

things, and is so in proportion, &c. Q.E.D.

 

PROP. XV. The idea, which constitutes the actual being of the

human mind, is not simple, but compounded of a great number of

ideas.

Proof.-The idea constituting the actual being of the human

mind is the idea of the body (II. xiii.), which (Post. i.) is

composed of a great number of complex individual parts. But

there is necessarily in God the idea of each individual part

whereof the body is composed (II. viii. Coroll.) ; therefore

(II. vii.), the idea of the human body is composed of these

numerous ideas of its component parts. Q.E.D.

 

PROP. XVI. The idea of every mode, in which the human body is

affected by external bodies, must involve the nature of the human

body, and also the nature of the external body.

Proof.-All the modes, in which any given body is affected,

follow from the nature of the body affected, and also from the

nature of the affecting body (by Ax. i., after the Coroll. of

Lemma iii.), wherefore their idea also necessarily (by I. Ax.

iv.) involves the nature of both bodies ; therefore, the idea of

every mode, in which the human body is affected by external

bodies, involves the nature of the human body and of the external

body. Q.E.D.

Corollary I.-Hence it follows, first, that the human mind

perceives the nature of a variety of bodies, together with the

nature of its own.

Corollary II.-It follows, secondly, that the ideas, which we

have of external bodies, indicate rather the constitution of our

own body than the nature of external bodies. I have amply

illustrated this in the Appendix to Part I.

 

PROP. XVII. If the human body is affected in a manner which

involves the nature of any external body, the human mind will

regard the said external body as actually existing, or as present

to itself, until the human body be affected in such a way, as to

exclude the existence or the presence of the said external body.

Proof.-This proposition is self-evident, for so long as the

human body continues to be thus affected, so long will the human

mind (II. xii.) regard this modification of the body-that is (by

the last Prop.), it will have the idea of the mode as actually

existing, and this idea involves the nature of the external body.

In other words, it will have the idea which does not exclude, but

postulates the existence or presence of the nature of the

external body ; therefore the mind (by II. xvi., Coroll. i.) will

regard the external body as actually existing, until it is

affected, &c. Q.E.D.

Corollary.-The mind is able to regard as present external

bodies, by which the human body has once been affected, even

though they be no longer in existence or present.

Proof.-When external bodies determine the fluid parts of the

human body, so that they often impinge on the softer parts, they

change the surface of the last named (Post. v.) ; hence (Ax. ii.,

after the Coroll. of Lemma iii.) they are refracted therefrom in

a different manner from that which they followed before such

change ; and, further, when afterwards they impinge on the new

surfaces by their own spontaneous movement, they will be

refracted in the same manner, as though they had been impelled

towards those surfaces by external bodies ; consequently, they

will, while they continue to be thus refracted, affect the human

body in the same manner, whereof the mind (II. xii.) will again

take cognizance-that is (II. xvii.), the mind will again regard

the external body as present, and will do so, as often as the

fluid parts of the human body impinge on the aforesaid surfaces

by their own spontaneous motion. Wherefore, although the

external bodies, by which the human body has once been affected,

be no longer in existence, the mind will nevertheless regard them

as present, as often as this action of the body is repeated.

Q.E.D.

Note.-We thus see how it comes about, as is often the case,

that we regard as present many things which are not. It is

possible that the same result may be brought about by other

causes ; but I think it suffices for me here to have indicated

one possible explanation, just as well as if I had pointed out

the true cause. Indeed, I do not think I am very far from the

truth, for all my assumptions are based on postulates, which

rest, almost without exception, on experience, that cannot be

controverted by those who have shown, as we have, that the human

body, as we feel it, exists (Coroll. after II. xiii.).

Furthermore (II. vii. Coroll., II. xvi. Coroll. ii.), we clearly

understand what is the difference between the idea, say, of

Peter, which constitutes the essence of Peter’s mind, and the

idea of the said Peter, which is in another man, say, Paul. The

former directly answers to the essence of Peter’s own body, and

only implies existence so long as Peter exists ; the latter

indicates rather the disposition of Paul’s body than the nature

of Peter, and, therefore, while this disposition of Paul’s body

lasts, Paul’s mind will regard Peter as present to itself, even

though he no longer exists. Further, to retain the usual

phraseology, the modifications of the human body, of which the

ideas represent external bodies as present to us, we will call

the images of things, though they do not recall the figure of

things. When the mind regards bodies in this fashion, we say

that it imagines. I will here draw attention to the fact, in

order to indicate where error lies, that the imaginations of the

mind, looked at in themselves, do not contain error. The mind

does not err in the mere act of imagining, but only in so far as

it is regarded as being without the idea, which excludes the

existence of such things as it imagines to be present to it. If

the mind, while imagining non-existent things as present to it,

is at the same time conscious that they do not really exist, this

power of imagination must be set down to the efficacy of its

nature, and not to a fault, especially if this faculty of