Sunday, August 07, 2005


One thing that bothers me about David Hume's Enquiry Concerning Human Understanding. On one hand, he is a thoroughgoing skeptic about the very possibility of causation. We have no idea what really amounts to causation; all we can really say is that one event follows another. Note especially the highlighted passages:
BUT to hasten to a conclusion of this argument, which is already drawn out to too great a length: we have sought in vain for an idea of power or necessary connexion in all the sources from which we could suppose it to be derived. It appears that, in single instances of the operation of bodies, we never can, by our utmost scrutiny, discover any thing but one event following another, without being able to comprehend any force or power by which the cause operates, or any connexion between it and its supposed effect. The same difficulty occurs in contemplating the operations of mind on body--where we observe the motion of the latter to follow upon the volition of the former, but are not able to observe or conceive the tie which binds together the motion and volition, or the energy by which the mind produces this effect. The authority of the will over its own faculties and ideas is not a whit more comprehensible: so that, upon the whole, there appears not, throughout all nature, any one instance of connexion which is conceivable by us. All events seem entirely loose and separate. One event follows another; but we never can observe any tie between them. They seem conjoined, but never connected. And as we can have no idea of any thing which never appeared to our outward sense or inward sentiment, the necessary conclusion seems to be that we have no idea of connexion or power at all, and that these words are absolutely, without any meaning, when employed either in philosophical reasonings or common life.

* * *
Even after one instance or experiment where we have observed a particular event to follow upon another, we are not entitled to form a general rule, or foretell what will happen in like cases; it being justly esteemed an unpardonable temerity to judge of the whole course of nature from one single experiment, however accurate or certain. But when one particular species of event has always, in all instances, been conjoined with another, we make no longer any scruple of foretelling one upon the appearance of the other, and of employing that reasoning, which can alone assure us of any matter of fact or existence. We then call the one object, Cause; the other, Effect. We suppose that there is some connexion between them; some power in the one, by which it infallibly produces the other, and operates with the greatest certainty and strongest necessity.

It appears, then, that this idea of a necessary connexion among events arises from a number of similar instances which occur of the constant conjunction of these events; nor can that idea ever be suggested by any one of these instances, surveyed in all possible lights and positions. But there is nothing in a number of instances, different from every single instance, which is supposed to be exactly similar; except only, that after a repetition of similar instances, the mind is carried by habit, upon the appearance of one event, to expect its usual attendant, and to believe that it will exist. This connexion, therefore, which we feel in the mind, this customary transition of the imagination from one object to its usual attendant, is the sentiment or impression from which we form the idea of power or necessary connexion. Nothing farther is in the case. Contemplate the subject on all sides; you will never find any other origin of that idea. This is the sole difference between one instance, from which we can never receive the idea of connexion, and a number of similar instances, by which it is suggested. The first time a man saw the communication of motion by impulse, as by the shock of two billiard balls, he could not pronounce that the one event was connected: but only that it was conjoined with the other. After he has observed several instances of this nature, he then pronounces them to be connected. What alteration has happened to give rise to this new idea of connexion? Nothing but that he now feels these events to be connected in his imagination, and can readily foretell the existence of one from the appearance of the other. When we say, therefore, that one object is connected with another, we mean only that they have acquired a connexion in our thought, and give rise to this inference, by which they become proofs of each other's existence: A conclusion which is somewhat extraordinary, but which seems founded on sufficient evidence. Nor will its evidence be weakened by any general diffidence of the understanding, or sceptical suspicion concerning every conclusion which is new and extraordinary. No conclusions can be more agreeable to scepticism than such as make discoveries concerning the weakness and narrow limits of human reason and capacity.

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 distant 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.
In other words, as I understand the above passage, Hume is saying: 1) When we observe a single event, we cannot possibly have any idea about cause and effect; 2) When we observe the same sequence of events happening numerous times, we start to talk about cause and effect; BUT 3) All of this talk is really due to how we view these events in our own "imagination"; in fact, we "have no idea" nor "even any distant notion" about cause and effect, of which it is "impossible to give any just definition."

But on the other hand, Hume is a thoroughgoing skeptic about the possibility of miracles:
A miracle is a violation of the laws of nature; and as a firm and unalterable experience has established these laws, the proof against a miracle, from the very nature of the fact, is as entire as any argument from experience can possibly be imagined. Why is it more than probable, that all men must die; that lead cannot, of itself, remain suspended in the air; that fire consumes wood, and is extinguished by water; unless it be, that these events are found agreeable to the laws of nature, and there is required a violation of these laws, or in other words, a miracle to prevent them? Nothing is esteemed a miracle, if it ever happen in the common course of nature. It is no miracle that a man, seemingly in good health, should die on a sudden: because such a kind of death, though more unusual than any other, has yet been frequently observed to happen. But it is a miracle, that a dead man should come to life; because that has never been observed in any age or country. There must, therefore, be a uniform experience against every miraculous event, otherwise the event would not merit that appellation. And as a uniform experience amounts to a proof, there is here a direct and full proof, from the nature of the fact, against the existence of any miracle; nor can such a proof be destroyed, or the miracle rendered credible, but by an opposite proof, which is superior.
Whoa. If it is "impossible" for us to understand cause and effect in the events of nature, why does Hume begin this passage with the insistence that a miracle is a "violation of the laws of nature"? Who says there are any such laws in the first place? According to Hume's first passage above, all we can say is that we have seen various events happening a number of times, but we can't really understand why. Who's to say that what we're observing is an instantiation of a law? Why should "uniform experience" amount to a "proof," if no one can really understand why that experience was uniform in the first place?

Also, by the way, note that Hume is begging the question in the second bolded passage above. He defines "miracle" as "something which has never been experienced," and then concludes -- what a surprise! -- that if no one has ever experienced a miracle, any testimony regarding a miracle must be untruthful. Yes indeed, but when the very question is whether anyone has ever experienced a miracle, playing with the definition of "miracle" won't answer the question.


Anonymous Anonymous said...

Hume also ended his book with a defense of book burning that it unintentionally ironic. He says:

"If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion."

Nevermind that the Enquiry doesn't contain either abstract reasoning concerning quantity or number or experimental reasoning concerning matters of fact and existence, and therefore, by his own criterion, ought to be destroyed.

2:21 PM  
Blogger Brandon said...

Hume has a broad notion of 'experimental reasoning', so would no doubt include his work under that category.

I don't think it's quite right to say that Hume is a skeptic about the possibility of causation; rather, it would be more accurate to say that he's a skeptic about whether we can say much more about causation than the fact that we treat some things as causes and effects. As he had noted in the Treatise, his account differs from other accounts in that they try to find the nature of causation in the objects themselves, while he tries to find it in causal inference. So I think Hume's argument should be interpreted as claiming that inferring miracles from testimony requires a form of reasoning that is aberrant compared to ordinary causal inferences. But you're right that it isn't clear that he succeeds in showing even this. You might find Whately's 19th-century parody of Hume's argument amusing:

Historic Doubts Relative to Napoleon Buonaparte

11:07 AM  
Blogger Hunter Baker said...

Brilliant, Stuart. I hadn't seen that point made about Hume before. It's knockdown. Great stuff.

3:00 PM  

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