An Enquiry Concerning Human Understanding, David Hume [online e book reader TXT] 📗

>such as make discoveries concerning the weakness and narrow limits of

human reason and capacity.

 

60. And what stronger instance can be produced of the surprising

ignorance and weakness of the understanding than the present? For

surely, if there be any relation among objects which it imports to us to

know perfectly, it is that of cause and effect. On this are founded all

our reasonings concerning matter of fact or existence. By means of it

alone we attain any assurance concerning objects which are removed from

the present testimony of our memory and senses. The only immediate

utility of all sciences, is to teach us, how to control and regulate

future events by their causes. Our thoughts and enquiries are,

therefore, every moment, employed about this relation: Yet so imperfect

are the ideas which we form concerning it, that it is impossible to give

any just definition of cause, except what is drawn from something

extraneous and foreign to it. Similar objects are always conjoined with

similar. Of this we have experience. Suitably to this experience,

therefore, we may define a cause to be _an object, followed by another,

and where all the objects similar to the first are followed by objects

similar to the second_. Or in other words _where, if the first object

had not been, the second never had existed_. The appearance of a cause

always conveys the mind, by a customary transition, to the idea of the

effect. Of this also we have experience. We may, therefore, suitably to

this experience, form another definition of cause, and call it, _an

object followed by another, and whose appearance always conveys the

thought to that other._ But though both these definitions be drawn from

circumstances foreign to the cause, we cannot remedy this inconvenience,

or attain any more perfect definition, which may point out that

circumstance in the cause, which gives it a connexion with its effect.

We have no idea of this connexion, nor even any distinct notion what it

is we desire to know, when we endeavour at a conception of it. We say,

for instance, that the vibration of this string is the cause of this

particular sound. But what do we mean by that affirmation? We either

mean _that this vibration is followed by this sound, and that all

similar vibrations have been followed by similar sounds:_ Or, _that this

vibration is followed by this sound, and that upon the appearance of one

the mind anticipates the senses, and forms immediately an idea of the

other._ We may consider the relation of cause and effect in either of

these two lights; but beyond these, we have no idea of it.[16]

 

[16] According to these explications and definitions, the idea

of power is relative as much as that of cause; and both

have a reference to an effect, or some other event constantly

conjoined with the former. When we consider the unknown

circumstance of an object, by which the degree or quantity of

its effect is fixed and determined, we call that its power: And

accordingly, it is allowed by all philosophers, that the effect

is the measure of the power. But if they had any idea of power,

as it is in itself, why could not they Measure it in itself?

The dispute whether the force of a body in motion be as its

velocity, or the square of its velocity; this dispute, I say,

need not be decided by comparing its effects in equal or

unequal times; but by a direct mensuration and comparison.

 

As to the frequent use of the words, Force, Power, Energy, &c.,

which every where occur in common conversation, as well as in

philosophy; that is no proof, that we are acquainted, in any

instance, with the connecting principle between cause and

effect, or can account ultimately for the production of one

thing to another. These words, as commonly used, have very

loose meanings annexed to them; and their ideas are very

uncertain and confused. No animal can put external bodies in

motion without the sentiment of a nisus or endeavour; and

every animal has a sentiment or feeling from the stroke or blow

of an external object, that is in motion. These sensations,

which are merely animal, and from which we can � priori draw

no inference, we are apt to transfer to inanimate objects, and

to suppose, that they have some such feelings, whenever they

transfer or receive motion. With regard to energies, which are

exerted, without our annexing to them any idea of communicated

motion, we consider only the constant experienced conjunction

of the events; and as we feel a customary connexion between

the ideas, we transfer that feeling to the objects; as nothing

is more usual than to apply to external bodies every internal

sensation, which they occasion.

 

61. To recapitulate, therefore, the reasonings of this section: Every

idea is copied from some preceding impression or sentiment; and where we

cannot find any impression, we may be certain that there is no idea. In

all single instances of the operation of bodies or minds, there is

nothing that produces any impression, nor consequently can suggest any

idea of power or necessary connexion. But when many uniform instances

appear, and the same object is always followed by the same event; we

then begin to entertain the notion of cause and connexion. We then

feel a new sentiment or impression, to wit, a customary connexion in

the thought or imagination between one object and its usual attendant;

and this sentiment is the original of that idea which we seek for. For

as this idea arises from a number of similar instances, and not from any

single instance, it must arise from that circumstance, in which the

number of instances differ from every individual instance. But this

customary connexion or transition of the imagination is the only

circumstance in which they differ. In every other particular they are

alike. The first instance which we saw of motion communicated by the

shock of two billiard balls (to return to this obvious illustration) is

exactly similar to any instance that may, at present, occur to us;

except only, that we could not, at first, infer one event from the

other; which we are enabled to do at present, after so long a course of

uniform experience. I know not whether the reader will readily apprehend

this reasoning. I am afraid that, should I multiply words about it, or

throw it into a greater variety of lights, it would only become more

obscure and intricate. In all abstract reasonings there is one point of

view which, if we can happily hit, we shall go farther towards

illustrating the subject than by all the eloquence and copious

expression in the world. This point of view we should endeavour to

reach, and reserve the flowers of rhetoric for subjects which are more

adapted to them.

 

SECTION VIII.

 

OF LIBERTY AND NECESSITY.

 

PART I.

 

62. It might reasonably be expected in questions which have been

canvassed and disputed with great eagerness, since the first origin of

science and philosophy, that the meaning of all the terms, at least,

should have been agreed upon among the disputants; and our enquiries, in

the course of two thousand years, been able to pass from words to the

true and real subject of the controversy. For how easy may it seem to

give exact definitions of the terms employed in reasoning, and make

these definitions, not the mere sound of words, the object of future

scrutiny and examination? But if we consider the matter more narrowly,

we shall be apt to draw a quite opposite conclusion. From this

circumstance alone, that a controversy has been long kept on foot, and

remains still undecided, we may presume that there is some ambiguity in

the expression, and that the disputants affix different ideas to the

terms employed in the controversy. For as the faculties of the mind are

supposed to be naturally alike in every individual; otherwise nothing

could be more fruitless than to reason or dispute together; it were

impossible, if men affix the same ideas to their terms, that they could

so long form different opinions of the same subject; especially when

they communicate their views, and each party turn themselves on all

sides, in search of arguments which may give them the victory over their

antagonists. It is true, if men attempt the discussion of questions

which lie entirely beyond the reach of human capacity, such as those

concerning the origin of worlds, or the economy of the intellectual

system or region of spirits, they may long beat the air in their

fruitless contests, and never arrive at any determinate conclusion. But

if the question regard any subject of common life and experience,

nothing, one would think, could preserve the dispute so long undecided

but some ambiguous expressions, which keep the antagonists still at a

distance, and hinder them from grappling with each other.

 

63. This has been the case in the long disputed question concerning

liberty and necessity; and to so remarkable a degree that, if I be not

much mistaken, we shall find, that all mankind, both learned and

ignorant, have always been of the same opinion with regard to this

subject, and that a few intelligible definitions would immediately have

put an end to the whole controversy. I own that this dispute has been so

much canvassed on all hands, and has led philosophers into such a

labyrinth of obscure sophistry, that it is no wonder, if a sensible

reader indulge his ease so far as to turn a deaf ear to the proposal of

such a question, from which he can expect neither instruction or

entertainment. But the state of the argument here proposed may, perhaps,

serve to renew his attention; as it has more novelty, promises at least

some decision of the controversy, and will not much disturb his ease by

any intricate or obscure reasoning.

 

I hope, therefore, to make it appear that all men have ever agreed in

the doctrine both of necessity and of liberty, according to any

reasonable sense, which can be put on these terms; and that the whole

controversy has hitherto turned merely upon words. We shall begin with

examining the doctrine of necessity.

 

64. It is universally allowed that matter, in all its operations, is

actuated by a necessary force, and that every natural effect is so

precisely determined by the energy of its cause that no other effect, in

such particular circumstances, could possibly have resulted from it. The

degree and direction of every motion is, by the laws of nature,

prescribed with such exactness that a living creature may as soon arise

from the shock of two bodies as motion in any other degree or direction

than what is actually produced by it. Would we, therefore, form a just

and precise idea of necessity, we must consider whence that idea

arises when we apply it to the operation of bodies.

 

It seems evident that, if all the scenes of nature were continually

shifted in such a manner that no two events bore any resemblance to each

other, but every object was entirely new, without any similitude to

whatever had been seen before, we should never, in that case, have

attained the least idea of necessity, or of a connexion among these

objects. We might say, upon such a supposition, that one object or event

has followed another; not that one was produced by the other. The

relation of cause and effect must be utterly unknown to mankind.

Inference and reasoning concerning the operations of nature would, from

that moment, be at an end; and the memory and senses remain the only

canals, by which the knowledge of any real existence could possibly have

access to the mind. Our idea, therefore, of