The empiricist philosopher David Hume never claimed that there’s nothing beyond experience. He argued, instead, that nothing can be known about it. Moreover, he believed that it’s idle to speculate about such things. He applied this way of thinking to all sorts of domains, including: science, mathematics, religion, aesthetics, morality, cause and effect, history... and even politics.
“If we take in our hand any volume of divinity or school metaphysics, for instance, let is ask, *Does it contain any abstract reasoning concerning quantity or number?* No. *Does it contain any experimental reasoning concerning matters of fact and existence?* No. Commit it then to the flames: for it can contain nothing but sophistry and illusion.”
— David Hume (From An Enquiry Concerning Human Understanding.)
Hume on the Ultimate Springs and Principles
Despite the title of this essay, David Hume did write about “the causes of these general causes” and concluded that
“[t]hese ultimate springs and principles are totally shut up from human curiosity and enquiry”.
Some readers may wonder why, according to his own logic, Hume believed in ultimate springs and principles at all. That’s asked because such things are, according to Hume himself, shut up from human curiosity and enquiry. Perhaps, then, Hume simply raised the possibility that such things exist. Yet he still believed that it’s fruitless to speculate about them. In Hume’s philosophy, then, they are cogs in a machine which serve no purpose.
All that said, Hume did actually refer to what he believed were “probably the ultimate causes and principles”. He even gave the following examples: “Elasticity, gravity, cohesion of parts, communication of motion by impulse [ ].” In basic terms, then, the ultimate causes and principles of all these things are beyond experience or observation. Thus, they’re beyond knowledge.
It’s also worth noting here that Hume’s more self-conscious and obvious general philosophy is in some ways like Isaac Newton’s philosophy of science. Indeed, often all one really needs to do is substitute Hume’s 18th-century term “impressions” (or “sense impressions”) for Newton’s earlier term “phenomena”.
In terms of concrete examples, then, Hume had a problem with such “hypothetical entities” as substance, vacuum, necessary connection, the self, etc. Similarly, Newton had a problem with such things as the aether, corpuscles and what he called “occult properties”.
But what a strange state of affairs this is, at least when it comes to Hume.
Hume was happily admitting that in physics we have such things as elasticity, gravity, cohesion of parts, and the communication of motion by impulse, yet their ultimate springs and principles are totally shut up from human curiosity and enquiry. More clearly, we observe elasticity, the effects of gravity, the cohesions of parts, and the communication of motion by impulse, yet we still don’t know the ultimate causes and principles of such things. In other words, we don’t know what gravity is, why parts cohere, what is (metaphorically) behind motion, etc.
Again, couldn’t Hume have simply bitten the bullet and stated that there is nothing behind these things? Yet, had he done so, then perhaps he’d have entered the domain of idealism. After all, if all we’ve got is what we can observe or experience, then that does seem to at least hint at idealism. [See note 1.]
Hume on Knowledge
Hume had his own take on knowledge. Basically, he believed that only the results of mathematics can be known. In Hume’s own words:
“[T]he sciences of quantity and numbers [can be] pronounces the only proper objects of knowledge and demonstration.”
This may seem like an odd use of the word “knowledge” in that, in the everyday sense, it’s usually facts that are said to be known (“knowledge is an awareness of facts”). One can say “I know that 2 plus 2 equals 4”. Yet one can also say that “I know that snow is white”. However, on Hume’s reading, the last example isn’t an example of knowledge in his strict — or particular — sense. More clearly, it can’t be demonstrated that snow is white in the way that the truth 2 + 2 = 4 can be demonstrated.
Here Hume basically meant proved by the word “demonstrated”. Thus, you can’t prove that snow must be white. In other words, providing a sample of white snow isn’t a proof that snow is (always) white. Indeed, providing a thousand samples of white snow won’t prove that snow must be white either.
Hume then went into more detail on the importance and relevance of demonstration or proof. He told his readers that “matters of facts and existence [ ] are evidently incapable of demonstration”. Hume showed that by bringing contradiction and negation into the picture. He stated: “Whatever is may not be.” Thus, it’s surely possible that snow could be black. Moreover, there’s no contradiction in saying that “Snow is black” or “Snow is not white”. We can certainly conceive of snow being black. [See note 2.]
Hume on Cause and Effect
Hume cited Adam as a (possible) proto-Rationalist. According to Hume’s Bible, Adam’s “rational faculties be supposed, at the very first, entirely perfect”. Yet he
“could not have inferred from the fluidity and transparency of water that it would suffocate him, or from the light and warmth of fire that it would consume him”.
If Adam’s pure Rationalist mind had been real, then he should have been able to do so. (Leibniz, as we’ll see, denied this conclusion.) According to Hume, had Adam adhered to the dictates of Rationalism, he would have either drowned or been burned alive.
In any case, at first glance it may seem odd how much time Hume focussed on cause and effect. Yet these two notions together provided the centrepiece of his philosophy — at least his philosophy as it is expressed in An Enquiry Concerning Human Understanding.
Hume also tied “reasonings concerning matters of fact [to] the relation of Cause and Effect”. And that tie was (again) at the centre of his empiricism. Hume told his readers that “[b]y means of that relation alone we can go beyond the evidence of our memory and senses”.
What Hume said about cause and effect must be set within the context of his stance against Rationalism (or against a priori knowledge). In the following, he set out his case clearly:
“We are apt to imagine that we could discover these effects by the mere operation of our reason, without experience. We fancy, that were we brought on a sudden into this world, we could at first inferred that one billiard ball would communicate motion to another upon impulse; and that we needed not to have waited for the event, in order to pronounce with certainty concerning it.”
It’s not obvious that many laypeople would ever believe that they could discover these effects by the mere operation of their reason, without experience. In fact, this is probably not something they’d even think about. What’s more, wouldn’t they need to remember the first time they came across a billiard ball, and then guessed what it would do when it hit the other?…
But that’s highly unlikely too.
So Hume’s “we” actually refers to rationalist philosophers. And even they wouldn’t have thought about this until they started to read philosophy. Yet, in a strong sense, a pure rationalist would still need to believe that if he had thought about a billiard ball and its impact on another ball (i.e., before reading any philosophy), he could have worked out (a priori) what would happen.
In any case, Hume made the obvious point that “every effect is a distinct event from its cause”. More importantly, the effect “could not be discovered in the cause”. In retrospect at least, it may seem remarkable that anyone ever thought otherwise.
If we return to Hume’s balls. Isn’t it obvious that the
“[m]otion 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”.
All that said, there are different types of rationalist. Gottfried Leibniz, for example, acknowledged the following:
“Although the senses are necessary for all our actual knowledge, they are not sufficient to provide it all, since they never give us anything but instances, that is particular or singular truths. But however many instances confirm a general truth, they do not suffice to establish universal necessity; for it does not follow that what has happened will always happen in the same way.”
Leibniz, qua rationalist, acknowledged that when it comes to a billiard ball’s impact on another billiard ball, the senses are required. However, experiencing the result of one billiard ball hitting another one doesn’t mean that we can immediately conclude that same result will happen the next time. (Here Hume was in agreement with Leibniz.) In order to make a judgement about that next time, and the time after that, we must reason about this particular or singular event. In other words, we can’t conclude that the same thing will happen again if we’re only relying on the senses or experience.
What’s more, Leibniz argued that we need to incorporate the notion of universal necessity into our reasoning. Yet universal necessity itself isn’t found in experience or discovered by the senses. This means that we have no right to believe that the same kind of thing will happen again unless we commit ourselves to (some kind of) universal necessity.
As stated, Hume would have agreed with Leibniz up to the point in which he brings in the metaphysical notion of universal necessity. As an empiricist, Hume rejected universal necessity outright. Or at least he believed that we can never have any knowledge of such a thing.
Hume also tied cause and effect to what he called “existence”.
Hume on Existence
Hume believed that a claim about any existent
“can only be proved by arguments from its cause or its effect; and these arguments are founded entirely on experience”.
This statement immediately screams atheism, or at least agnosticism.
Of course, believers would say that they do experience God. However, Hume would simply have said that we can’t know that it’s God that they’re actually experiencing.
So statements about God or other questionable existents, then, are the result of “reasoning a priori”. If we move beyond God, and if we reason a priori, then “anything may appear able to produce anything”. Isn’t this the primary reason why anything goes in metaphysics? (Kant: Plato, like a “dove in free flight”, soared into the “empty space of pure understanding” on the wings of ideas.) Hume then cited an extreme metaphysical example (or at least an extreme example). If we reason a priori, “[t]he falling of a pebble may, for aught we know, extinguish the sun; or the wish of a man control the planets in their orbits”.
Here we can see an early stress on the importance of what we can and cannot conceive — that is, on the importance of conceivability.
God has just been mentioned. Hume goes on to state that
“[t]he non-existence of any being, without exception, is as clear and distinct an ideas as its existence”.
So here we’ve moved on from conceiving of snow being black, or to snow not existing at all. What’s more, we’ve moved on to the possibility of God not existing.
We can also see that “clear and distinct ideas” were as important to Hume as they were to Descartes before him.
The philosopher Saul Kripke, over 200 years later, stressed that we can’t imagine a true proposition being false. We may believe that we can do so. However, in actual fact, we don’t do so. More famously, Kripke cited an act of imagination (i.e., he didn’t use the word “conceiving”) which may mislead us. He wrote:
“[W]e thought erroneously that we could imagine a situation in which heat was not the motion of molecules. Because although we can say that we pick out heat contingently by the contingent property that it affects us in such and such way.”
Similarly, Hume stated that
“the cube root of 64 is equal to the half of 10 is a false proposition, and can never be distinctively conceived”.
A person may conceive something. However, what he’s conceiving can’t be 5 being the cube root of 64. He may well conceive of the number 5 and the number 64. And he may even carry out some mathematical operations. However, he can never genuinely conceive of the cube root of 64 being equal to the half of 10.
Hume on Morals and Aesthetics
Hume applied his empiricism across the board (but not to mathematics!). This meant that “morals” and aesthetics were placed under the scalpel of empiricism too. Or as Hume himself put it:
“Morals and criticism are not so properly objects of the understanding as of taste and sentiment.”
Here the “understanding” is deemed to be that which needn’t require experience or observation. To Hume’s opponents (mainly Rationalists), this meant that judgements about morals and criticism were deemed to be entirely due to what goes on in the human soul. Hume, on the other hand, deemed them to be a matter of taste and sentiment. And taste and sentiment are empirical matters in that they can be explained in terms of human psychology, society, matters of fact, history, etc.
Hume then singled out beauty when he told his readers that
“[b]eauty, whether moral or natural, is felt, more properly than perceived”.
Hume deemed feeling to be an empirical matter too.
So beauty is tied to feeling. As Hume put it:
“[I]f we reason concerning it, and endeavour to fix its standard, we regard a new fact, to wit, the general tastes of mankind, or some such fact, which may be the object of reasoning and enquiry.”
When someone asks, “What is beauty?”, Hume believed that the answer must bring in facts: facts about the general tastes of mankind or some such fact. In other words, we can’t answer this question simply by using our understanding. However, once we know the facts regarding the nature of beauty, then understanding can indeed be employed. Or at least we can reason and enquire about the facts which are relevant to any discussion about beauty.
One may ask why when a person answers the question “What is beauty?”, he or she is excluded from answering in an entirely subjective or personal way. A way that has nothing to do with the general tastes of mankind. In a Wittgensteinian manner, Hume might have argued that there’s no such thing as private beauty — or at least a private definition of beauty. There must be public criteria as to what beauty is. In other words, when answering the question, “What is beauty?”, the tastes of mankind or some such fact must become part of the answer.
Notes:
(1) If idealism were the game, then perhaps we couldn’t even say that we observe the effects of gravity, motion, etc. because that word doesn’t seem apt for things which belong exclusively to the subject’s mind or consciousness.
(2) Even though we can conceive of snow being black (contra Kripke?), whiteness can be seen as being a necessary property of snow. After all, chemically this can easily be explained. However, that chemical explanation still wouldn’t stop us from conceiving of black snow. (“Snow appears white because it is made of countless tiny ice crystals that are mostly air and reflect sunlight in all directions. While individual ice crystals are transparent, the multiple surfaces of these crystals scatter and refract the light, sending all the colors of the visible spectrum back to our eyes, which we perceive as white light.”)
