IN 1737 appeared Hume's Treatise of Human Nature, written from the standpoint of universal scepticism which was the basis of all his philosophy. This was shortly followed by Essays, Moral and Political, which, published in 1741-42, had a great success. In these Essays Hume brings to bear the results of his criticism upon the problems of current speculative discussion. The argument against miracles is still often discussed, and the work is well worthy of the author, whom many regard as the greatest thinker of his time. Hume's History of England (1754-62) enjoyed great fame, but owing to the author's prejudices and the inadequate material from which he worked is useless to the student.
[DOUBTS CONCERNING THE UNDERSTANDING - DAVID HUME - FROM ESSAYS, MORAL AND POLITICAL]
ALL the objects of human reason or inquiry may naturally be divided into two kinds--to wit, relations of ideas and matters of fact. Of the first kind are the sciences of geometry, algebra and arithmetic, and, in short, every affirmation which is either intuitively or demonstratively certain. 'That the square of the hypotenuse is equal to the squares of the two sides' is a proposition which expresses a relation between these figures. 'That three times five is equal to the half of thirty' expresses a relation between these numbers.
Propositions of this kind are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe. Though there never were a circle or triangle in nature, the truths demonstrated by Euclid would for ever retain their certainty and evidence.
Matters of fact, which are the second objects of human reason, are not ascertained in the same manner; nor is our evidence of their truth, however great, of a like nature with the foregoing. The contrary of every matter of fact is still possible because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness as if ever so conformable to reality. 'That the sun will not rise to-morrow' is no less intelligible a proposition, and implies no more contradiction, than the affirmative that 'it will rise.' We should in vain, therefore, attempt to demonstrate its falsehood. Were it demonstratively false, it would imply a contradiction and could never be distinctly conceived by the mind.
It may, therefore, be a subject worthy of curiosity to inquire what is the nature of that evidence which assures us of any real existence of matters of fact beyond the present testimony of our senses, or the records of our memory. All reasonings concerning matter of fact seem to be founded on the relation of cause and effect. If we would satisfy ourselves, therefore, concerning the nature of that evidence which assures us of matters of fact, we must inquire how we arrive at the knowledge of cause and effect.
I shall venture to affirm, as a general proposition which admits of no exception, that the knowledge of this relation is not, in any instance, attained by reasonings a priori, but arises entirely from experience.
To convince us that all the 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 examination. For the effect is totally different from the cause, and, consequently can never be discovered in it.
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?
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 be pretend to infer any cause or effect, without the assistance of observation and experience.
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.
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.
The bread which I formerly ate 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 a 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 you must confess that the inference is not intuitive; neither is it demonstrative. Of what nature is it, then? To say it is experimental is beggining the question. For all inferences from experience suppose, as their foundation, that the future will resemble the past and that similar powers will be conjoined with similar sensible qualities.
If there be any suspicion that the course of nature may change and that the past may be no rule for the future, all experience becomes useless and can give rise to no inference or conclusion. It is impossible, therefore, that any arguments from experience can prove this resemblance of the past to the future, since all these arguments are founded on the supposition of that resemblance. Let the course of things be allowed hitherto ever so regular, that alone, without some new argument or inference, proves not that for the future it will continue so.
In vain do you pretend to have learnt the nature of bodies from your past experience. Their secret nature, and consequently all their effects and influence, may change without any change in their sensible qualities. This happens sometimes, and with regard to some objects. Why may it not happen always, and with regard to all objects? What logic, what process of argument, secures you against this supposition?
MY practice, you say, refutes my doubts. But you mistake the purport of my question. As an agent, I am quite satisfied on the point; but as a philosopher, who has some share of curiosity, I will not say scepticism, I want to learn the foundation of this inference.
All inferences from experience are effects of custom, not of reasoning. We have already observed that nature has established connexions among particular ideas, and that no sooner one idea occurs to our thoughts than it introduces its correlative, and carries our attention towards it by a gentle and insensible movement. These principles of connexion or association we have reduced to three--namely, resemblance, contiguity and causation, which are the only bonds that unite our thoughts together and beget that regular train of reflection or discourse which, in a greater or less degree, takes place among mankind.
Now, here arises a question on which the solution of the present difficulty will depend. Does it happen in all these relations that when one of the objects is presented to the senses or memory the mind is not only carried to the conception of the correlative, but reaches a steadier and stronger conception of it than otherwise it would have been able to attain? This seems to be the case with that belief which arises from the relation of cause and effect.
And I shall add that it is conformable to the ordinary wisdom of nature to secure so necessary an act of the mind by some instinct or mechanical tendency, which may be infallible in its operations, may discover itself at the first appearance of thought, and may be independent of the laboured deductions of the understanding.
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