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

laws of nature, and all the

operations of bodies without exception, are known only by experience,

the following reflections may, perhaps, suffice. Were any object

presented to us, and were we required to pronounce concerning the

effect, which will result from it, without consulting past observation;

after what manner, I beseech you, must the mind proceed in this

operation? It must invent or imagine some event, which it ascribes to

the object as its effect; and it is plain that this invention must be

entirely arbitrary. The mind can never possibly find the effect in the

supposed cause, by the most accurate scrutiny and examination. For the

effect is totally different from the cause, and consequently can never

be discovered in it. Motion in the second Billiard-ball is a quite

distinct event from motion in the first; nor is there anything in the

one to suggest the smallest hint of the other. A stone or piece of metal

raised into the air, and left without any support, immediately falls:

but to consider the matter a priori, is there anything we discover in

this situation which can beget the idea of a downward, rather than an

upward, or any other motion, in the stone or metal? And as the first

imagination or invention of a particular effect, in all natural

operations, is arbitrary, where we consult not experience; so must we

also esteem the supposed tie or connexion between the cause and effect,

which binds them together, and renders it impossible that any other

effect could result from the operation of that cause. When I see, for

instance, a Billiard-ball moving in a straight line towards another;

even suppose motion in the second ball should by accident be suggested

to me, as the result of their contact or impulse; may I not conceive,

that a hundred different events might as well follow from that cause?

May not both these balls remain at absolute rest? May not the first ball

return in a straight line, or leap off from the second in any line or

direction? All these suppositions are consistent and conceivable. Why

then should we give the preference to one, which is no more consistent

or conceivable than the rest? All our reasonings a priori will never

be able to show us any foundation for this preference.

 

In a word, then, every effect is a distinct event from its cause. It

could not, therefore, be discovered in the cause, and the first

invention or conception of it, a priori, must be entirely arbitrary.

And even after it is suggested, the conjunction of it with the cause

must appear equally arbitrary; since there are always many other

effects, which, to reason, must seem fully as consistent and natural. In

vain, therefore, should we pretend to determine any single event, or

infer any cause or effect, without the assistance of observation and

experience.

 

26. Hence we may discover the reason why no philosopher, who is rational

and modest, has ever pretended to assign the ultimate cause of any

natural operation, or to show distinctly the action of that power, which

produces any single effect in the universe. It is confessed, that the

utmost effort of human reason is to reduce the principles, productive of

natural phenomena, to a greater simplicity, and to resolve the many

particular effects into a few general causes, by means of reasonings

from analogy, experience, and observation. But as to the causes of these

general causes, we should in vain attempt their discovery; nor shall we

ever be able to satisfy ourselves, by any particular explication of

them. These ultimate springs and principles are totally shut up from

human curiosity and enquiry. Elasticity, gravity, cohesion of parts,

communication of motion by impulse; these are probably the ultimate

causes and principles which we shall ever discover in nature; and we may

esteem ourselves sufficiently happy, if, by accurate enquiry and

reasoning, we can trace up the particular phenomena to, or near to,

these general principles. The most perfect philosophy of the natural

kind only staves off our ignorance a little longer: as perhaps the most

perfect philosophy of the moral or metaphysical kind serves only to

discover larger portions of it. Thus the observation of human blindness

and weakness is the result of all philosophy, and meets us at every

turn, in spite of our endeavours to elude or avoid it.

 

27. Nor is geometry, when taken into the assistance of natural

philosophy, ever able to remedy this defect, or lead us into the

knowledge of ultimate causes, by all that accuracy of reasoning for

which it is so justly celebrated. Every part of mixed mathematics

proceeds upon the supposition that certain laws are established by

nature in her operations; and abstract reasonings are employed, either

to assist experience in the discovery of these laws, or to determine

their influence in particular instances, where it depends upon any

precise degree of distance and quantity. Thus, it is a law of motion,

discovered by experience, that the moment or force of any body in motion

is in the compound ratio or proportion of its solid contents and its

velocity; and consequently, that a small force may remove the greatest

obstacle or raise the greatest weight, if, by any contrivance or

machinery, we can increase the velocity of that force, so as to make it

an overmatch for its antagonist. Geometry assists us in the application

of this law, by giving us the just dimensions of all the parts and

figures which can enter into any species of machine; but still the

discovery of the law itself is owing merely to experience, and all the

abstract reasonings in the world could never lead us one step towards

the knowledge of it. When we reason a priori, and consider merely any

object or cause, as it appears to the mind, independent of all

observation, it never could suggest to us the notion of any distinct

object, such as its effect; much less, show us the inseparable and

inviolable connexion between them. A man must be very sagacious who

could discover by reasoning that crystal is the effect of heat, and ice

of cold, without being previously acquainted with the operation of these

qualities.

 

PART II.

 

28. But we have not yet attained any tolerable satisfaction with regard

to the question first proposed. Each solution still gives rise to a new

question as difficult as the foregoing, and leads us on to farther

enquiries. When it is asked, _What is the nature of all our reasonings

concerning matter of fact?_ the proper answer seems to be, that they are

founded on the relation of cause and effect. When again it is asked,

_What is the foundation of all our reasonings and conclusions concerning

that relation?_ it may be replied in one word, Experience. But if we

still carry on our sifting humour, and ask, _What is the foundation of

all conclusions from experience?_ this implies a new question, which may

be of more difficult solution and explication. Philosophers, that give

themselves airs of superior wisdom and sufficiency, have a hard task

when they encounter persons of inquisitive dispositions, who push them

from every corner to which they retreat, and who are sure at last to

bring them to some dangerous dilemma. The best expedient to prevent this

confusion, is to be modest in our pretensions; and even to discover the

difficulty ourselves before it is objected to us. By this means, we may

make a kind of merit of our very ignorance.

 

I shall content myself, in this section, with an easy task, and shall

pretend only to give a negative answer to the question here proposed. I

say then, that, even after we have experience of the operations of cause

and effect, our conclusions from that experience are not founded on

reasoning, or any process of the understanding. This answer we must

endeavour both to explain and to defend.

 

29. It must certainly be allowed, that nature has kept us at a great

distance from all her secrets, and has afforded us only the knowledge of

a few superficial qualities of objects; while she conceals from us those

powers and principles on which the influence of those objects entirely

depends. Our senses inform us of the colour, weight, and consistence of

bread; but neither sense nor reason can ever inform us of those

qualities which fit it for the nourishment and support of a human body.

Sight or feeling conveys an idea of the actual motion of bodies; but as

to that wonderful force or power, which would carry on a moving body for

ever in a continued change of place, and which bodies never lose but by

communicating it to others; of this we cannot form the most distant

conception. But notwithstanding this ignorance of natural powers[6] and

principles, we always presume, when we see like sensible qualities, that

they have like secret powers, and expect that effects, similar to those

which we have experienced, will follow from them. If a body of like

colour and consistence with that bread, which we have formerly eat, be

presented to us, we make no scruple of repeating the experiment, and

foresee, with certainty, like nourishment and support. Now this is a

process of the mind or thought, of which I would willingly know the

foundation. It is allowed on all hands that there is no known connexion

between the sensible qualities and the secret powers; and consequently,

that the mind is not led to form such a conclusion concerning their

constant and regular conjunction, by anything which it knows of their

nature. As to past Experience, it can be allowed to give direct and

certain information of those precise objects only, and that precise

period of time, which fell under its cognizance: but why this experience

should be extended to future times, and to other objects, which for

aught we know, may be only in appearance similar; this is the main

question on which I would insist. The bread, which I formerly eat,

nourished me; that is, a body of such sensible qualities was, at that

time, endued with such secret powers: but does it follow, that other

bread must also nourish me at another time, and that like sensible

qualities must always be attended with like secret powers? The

consequence seems nowise necessary. At least, it must be acknowledged

that there is here a consequence drawn by the mind; that there is a

certain step taken; a process of thought, and an inference, which wants

to be explained. These two propositions are far from being the same, _I

have found that such an object has always been attended with such an

effect_, and _I foresee, that other objects, which are, in appearance,

similar, will be attended with similar effects_. I shall allow, if you

please, that the one proposition may justly be inferred from the other:

I know, in fact, that it always is inferred. But if you insist that the

inference is made by a chain of reasoning, I desire you to produce that

reasoning. The connexion between these propositions is not intuitive.

There is required a medium, which may enable the mind to draw such an

inference, if indeed it be drawn by reasoning and argument. What that

medium is, I must confess, passes my comprehension; and it is incumbent

on those to produce it, who assert that it really exists, and is the

origin of all our conclusions concerning matter of fact.

 

[6] The word, Power, is here used in a loose and popular sense.

The more accurate explication of it would give additional

evidence to this argument. See Sect. 7.

 

30. This negative argument must certainly, in process of time, become

altogether convincing, if many penetrating and able philosophers shall

turn their enquiries this way and no one be ever able