I shall venture to affirm, as a general proposition, which admits of no exception, that the knowledge of this relation [cause and effect] is not, in any instance, attained by reasonings a priori;but arises entirely from experience, when we find, that any particular object are constantly conjoined with each other. [From Enquiry Concerning Human Understanding]

Are you feeling sort of breathless after reading that passage? Don't worry—it's just all those commas I love to sprinkle my sentences with. Take a couple of deep breaths, and we'll get down to business.

This is the initial part of my famous critique of causality. I claim that all of our knowledge about the world is based on our knowledge of cause and effect—and all of that knowledge is based only on experience, on observation.

Imagine you have never seen a billiard ball—or anything at all like a billiard ball—before. My point is that you could think hard about the concept of a billiard ball, and you could endlessly contemplate its essence, but still you wouldn't have the faintest idea what to expect when one ball strikes another.

For all you know in your prior-to-experience state, the second ball will stay stationary or even disappear in a poof of smoke when struck by the first. It's only after repeated observations of the actual event sequence—the first ball hitting the second, the second moving—that we come to form the idea of a causal connection here. And so my initial conclusion is that our knowledge of causality is nothing more than the constant conjunction of two events.

You could say that for me there is less to causality than meets the eye.

I say, then, that, even after we have experience of the operation of cause and effect, our conclusions from that experience are not founded on any reasoning, or any process of the understanding. [From Enquiry Concerning Human Understanding]

This is me at my wackiest and most skeptical. Are you intrigued?

Okay, so we know that our knowledge of causality is entirely based on experience. What, then, is the basis of all the conclusions we draw on that experience? In other words, on what basis do we make causal claims about what will happen in the future? My answer will shock and amaze you: There is no basis whatsoever! This is what's sometimes referred to (rather dryly for my taste) as "Hume's problem of induction," though I myself never use the term "induction" in this way.

Let's go back to the billiard balls we talked about in the last quote. So, we have seen the constant conjunction of the motion of these balls and concluded that the first one causes the second to move. Now, I predict that the next time ball A strikes ball B, ball B will move.

My reasoning seems pretty clear: I have observed that whenever ball A has struck ball B in the past, ball B has always moved. Therefore, I conclude that in the future, when ball A strikes ball B, ball B will move again. Okay, great—but what justifies this inference? How do I get from a claim about what has happened in the past to a claim about what will happen in the future? It seems I have to add another assumption here—the claim that the future will always resemble the past.

Sounds fine, right? But wait a minute: will the future always resemble the past? That's what I have to assume to justify this inference, but that's just what the whole argument is supposed to be proving in the first place. This argument is circular! That means that there is absolutely no reason to suppose this billiard ball will move the next time it is struck. And so it seems that there is no basis, no foundation at all for our most basic beliefs about the regularities of nature—the very things that we depend on every day. Anything, anything at all, no matter how strange or unexpected, is possible.

So that, upon the whole, we may conclude that the Christian Religion not only was at first attended with miracles, but even at this day cannot be believed by any reasonable person without one. Mere reason is insufficient to convince us of its veracity. [From Enquiry Concerning Human Understanding]

That doesn't mean I believe in miracles, though. A miracle, I claim, is a violation of the laws of nature. And since the laws of nature are based entirely on experience, on the observation of what always has been observed to happen, a miracle by its very nature is all but impossible. Translation: since the laws of nature are no more than summaries of what usually happens, it's unlikely they are going to be violated.

I am saying here, then, that since Christianity depends on the occurrence of miracles, it would be a miracle if anyone actually believed it.

Now, there are some who have taken this as a wonderful expression of the notion of religious faith. There is no rational basis to Christianity, I am taken to argue, and so it depends on a faith whose existence is the greatest miracle of all. But to these overly clever readers I say: better adjust your snark meters. Sorry, I am not trying to explain how acceptance of religion is possible. I'm basically saying you'd have to be nuts to believe this stuff.

It is sufficient for our present purpose, if it be allowed, what surely, without the greatest absurdity, cannot be disputed, that there is some benevolence, however small, infused into our bosom; some spark of friendship for human kind; some particle of the dove, kneaded into our frame, along with the elements of the wolf and the dove. Let these generous sentiments be supposed ever so weak; let them be insufficient to move even a hand or finger of our body; they must still direct the determinations of our mind, and where every thing else is equal, produce a cool preference of what is useful and serviceable to mankind, above what is pernicious and dangerous. A moral distinction, therefore, immediately arises; a general sentiment of blame and approbation, a tendency, however faint, to the objects of the one, and a proportionable aversion […]" [From Enquiry Concerning the Principles of Morals]

Okay, I know: my literary ambitions sometimes get the better of my desire for clarity. But you can't deny the beauty of that prose, can you? What I'm getting at here is the basis for my whole moral theory. I claim that there is, in all of us, a natural tendency to care about others and therefore to like and approve of virtuous behavior, on the one hand, and to dislike and disapprove of negative behavior, on the other.

Now, I'm a realist. I'm not saying we're all saints and that we will all sacrifice our self-interest for others; I'm only claiming that we have the smallest concern for others. But these natural sentiments are enough to predispose us to favor virtue over vice—and thereby to make morality possible.

Thus, though the principles of taste be universal, and, nearly, if not entirely the same in all men; yet few are qualified to give judgment on any work of art, or establish their own sentiment as the standard of beauty. The organs of internal sensation are seldom so perfect as to allow the general principles their full play, and produce a feeling correspondent to those principles. They either labour under some defect, or are vitiated by some disorder; and by that means, excite a sentiment, which may be pronounced erroneous. When the critic has no delicacy, he judges without any distinction, and is only affected by the grosser and more palpable qualities of the object: The finer touches pass unnoticed and disregarded. Where he is not aided by practice, his verdict is attended with confusion and hesitation. [From "Of the Standard of Taste"]

I can already hear your response to this one: "Hold on a hot minute, partner. You say there are universal principles of taste, but at the same time, you say that people's aesthetic judgments are usually erroneous? That's a pretty peculiar idea of 'universal' you're working with there, David."

You are to be forgiven if you imagine that I am speaking out of both sides of my mouth at the same time here. But, look, this is just an extension of my moral theory. Like moral judgments, aesthetic judgments are based not in reason or in intuition, but in sentiments. These sentiments are essentially the same in all people.

Therefore, we can establish basic rules about how literature (and art in general) does and does not properly please us, which is to say that we can establish basic rules about what is good and bad aesthetically. That's right: there are standards of art; it's not just a matter of subjective preference.

But—you knew there was a "but" coming, didn't you?—just because these standards can be established, it doesn't mean that in practice, we'll all actually reach the same verdict about the value of a work of art. Why is that?

Well, I say that while our aesthetic responses are the same under ideal conditions, in reality they can be skewed by all sorts of factors. So, some people, by disposition, are incapable of responding to certain kinds of writing. There are those, for example, who don't get humor. There are also those who don't have enough experience with literature to be able to render any appropriate judgments about a text; their tastes are simply too crude and unformed. And so on.

The point is that by nature, we all only have the capacity to make good aesthetic judgments. Taste, just like any other skill, needs to be trained and developed. In short, for me to say that there are universal principles of taste means only that the normal, properly educated reader will respond to a text, under normal conditions, in certain predictable ways.