Dr Tom Kerns
North Seattle Community College



David Hume


(This lecture is a longish one; you may want to print it out for reading)

David Hume's thought and writings are most interesting and have been extremely influential, both in the philosophical world and in the world of the sciences, but we are going to look briefly at only two of his ideas. These two ideas, the notion of cause and effect, and the concept of self or identity, are central to Hume's thought, but if you thought that Berkeley was a tough sell, Hume's ideas may be even more difficult for you to accept.

His first book, A Treatise of Human Nature, was published in 1738 when he was only 27. It's a big book and quite clearly written, but no one in the philosophical world read it. "It fell deadborn from the press," Hume wrote some years later. Not one review was written about that book for years after it came out. Eventually one short review of it was published several years later in an obscure philosophical journal, written by a philosopher no one had ever heard of. The review said basically that the book was not so terribly written, that some of the ideas in it were somewhat interesting, but that overall it had obviously been written by a youthful and not-yet-mature intellect, and that it didn't really deserve the time that it would take for anyone to read it. That was the one published review of the Treatise.

(Only a few decades ago it was somehow discovered that Hume himself wrote that review and submitted it to the journal under an assumed name.)

Because that book had been such a failure at gaining any readers, Hume decided to recast the whole of it into a much shorter and more palatable book, An Enquiry Concerning Human Understanding, published ten years later in 1748 when he was 37 years old.

Hume's analysis of the notion of cause and effect was so central to his thought that it is dealt with in both his books, but the concept of self which was dealt with in the Treatise was not carried over into the Enquiry. Hume apparently believed that people would find that idea so unpalatable that it would be best if he just left it where it was, in the Treatise.

For our purposes here we will deal first with Hume's analysis of cause and effect, and secondly with his notion of self.

I. Cause and effect

The idea that events are caused, i.e., that they do not just happen randomly, is one of the cornerstones of our worldview. We believe that events do not "just happen," but that some set of causes has brought each event about. We believe that even if we do not know what the causes are for a given event, still some cause or causes must have brought this event into being. Every time we ask "Why?" the appropriate response is "Because" When we ask why something happened, we are asking for its causes, and the reason we even ask about causes is because we have an implicit belief that nothing happens without being caused.

This belief is one of the absolutely essential fundamental underpinnings of our entire worldview. So fundamental is this belief that if it were to be somehow undermined, much of our entire worldview could suddenly become highly doubtful.

John Locke wrote about the external world's qualities causing our sensations and perceptions, and Berkeley wrote about God being the cause of our perceptions, so it was natural for Hume to ask what it meant to say that one thing causes another.

When we say that one event causes another - for example, flipping the light switch causes the light to go on - we are, according to Hume, claiming that there is some "necessary connection" between flipping the light switch and the light going on. When we say that event A "causes" event B, we are saying that event A and event B are not just accidentally occurring next to each other in time, but that the two events are connected with each other in some necessary way.

If one moment I absent-mindedly scratch my ear and the next moment a bird smashes into my window, I'm not likely to think those two events are causally connected. I would probably not say that one event caused the other. I am more likely to say that the two events - first scratching my ear and then immediately afterwards a bird hitting the window - just happened to be immediately contiguous with each other. We would likely say that those two events are simply contiguous events, not necessarily connected (or causally connected) events.

What Hume wants us to consider here is where our idea of cause and effect comes from. He suspects that it may simply be an inherited idea that we've accepted without examination, and he proposes that we examine it closely. We should look to see if we ever actually experience cause and effect, or if it's just an idea that was made up somewhere and we've just accepted it ever since. So Hume asks us to look very closely at our experience to see if we truly do experience causing going on. If we don't, that is, if the idea has absolutely no basis in direct experience, then it should be thrown out, as should all ideas that have no basis in experience.

Perhaps a story can help us here, a story that is true (as best as I remember it) and is in any case highly illustrative.

Thirty-five or forty years ago there was a major power failure in New York City and all the lights in the entire city went out. It happened late on an autumn afternoon just about dusk, and the power failure lasted for many hours. (Exactly nine months later all the local hospitals were literally overwhelmed with OB admissions.) On the afternoon in question, a little four year old boy was playing out in his front yard. On this particular afternoon, the boy was testing his limits by venturing out toward the telephone pole at the far edge of the front yard. His mother had always told him to never go near the telephone pole (perhaps it was so that he would not go outside the yard). But what he had always heard his mother say was "Never touch the telephone pole," so of course he never had. But on this particular afternoon his mother was not watching him quite as closely as she normally did, and he was slowly sneaking over toward the pole to see if maybe he could get away with touching the forbidden pole. He finally noticed a moment when his mother was not watching and he went over and touched the pole. And at that instant all the lights in New York City went out.

The boy then "knew," of course, why his mother had told him to never touch the pole. Touching the pole had obviously caused all the lights in the city to go out. As much as his parents consoled him later, and as much as they assured him that his touching the pole had not caused all the lights to go out, still he "knew" and believed that his touching the pole had caused all the lights go out.

Now this association of two events (touching the pole and all the lights going out) is actually much like every other case in which we associate two events and believe that one caused the other. What Hume would want us to do, however, is to closely examine whether we just theorize and then believe that event A caused event B (like the little boy did), or whether we actually experience event A causing event B.

Hume's claim is that, like the little boy, we do not actually experience the causing going on. All we ever experience is that first one event occurs (touching the pole) and then immediately following it another event occurs (the lights go out). We never experience the first event actually doing the causing. We never experience the "necessary connection" between the two events. Instead, no matter how many times the two events occur contiguously with each other, we still never directly experience any actual causing. All we actually ever experience is events that are "regularly contiguous" with each other. Even though we may want to believe that one event makes another event happen, still we never experience the making going on between the first event and the second.

Now suppose we extend our story just a bit further: The little boy grows up with an enormous sense of guilt for having touched the pole, for having caused all the city's lights to go out, and for having caused all those thousands of new births, etc. He is distressed by this memory for years, and eventually has to go into therapy for it. His therapist works with him for years, all to no avail. Finally the therapist tells the young man that he will never get over this guilt and anxiety until he again goes out to that same telephone pole and physically touches it one more time. Then he will see that touching the pole does not cause the lights to go out. So he and the therapist go out to the old neighborhood, find the exact same telephone pole, and with much fear and trembling the young man slowly walks toward the pole. When he finally gets close to it, with much anxiety he slowly reaches out touches the pole.

And again all the lights in New York City go out. (The lights did actually go out a second time years later, but I've fabricated the stuff about the boy and his therapist.) So now the boy is absolutely convinced that touching the pole makes the lights go out, and again he is overcome with anxiety and guilt. We can only guess what becomes of him in the rest of his life, but we can be sure that he never lets go of his belief that touching the pole caused the lights to go out, no matter what rational people tell him.

Hume believes that we are all the same way. We continue to go on believing in the existence of cause and effect even though no one has ever experienced causing happening, and even though rational people (like Hume, Kant, Schopenhauer, etc) continue to show us that the whole idea of cause and effect is merely a theoretical construct made up in human minds. It has, these Philosophers assure us, absolutely no basis in experience.

Now this is only a very skeletal summary of Hume's position. The arguments which provide the foundation for this position are spelled out very clearly in his Enquiry Concerning Human Understanding, and are readily accessible to anyone interested in reading them. But if Hume is correct in this assessment of the idea of cause and effect, this is significant indeed. Many of the sciences, for example, which have seen their primary work as "the search for causes," would find themselves in need of re-definition if Hume is correct.

Immanuel Kant writes, some years later, that reading David Hume was a very powerful experience for him, and that reading Hume's writings "woke me from my dogmatic slumbers." Many others who read Hume find it to have the same effect on them.

II. Self

What is a self, an identity, a mind, and where does the idea of such a thing even come from? Locke believed in the existence of minds, and so did Berkeley. Now Hume is going to wonder what a mind, or self, is.

This question was not new even in Hume's time. The ancients had raised the question in the following way:.

In ancient Greece there was a famous ship tied up in the harbor so that people could come see it and could bring their children to walk on its decks (much like today people want to walk on the USS Missouri, or on the ship on which their father fought in WWII, etc). This ship was famous because it had fought in an important battle. Over the years, however, as the ship aged, its rigging had to be replaced, and then its masts had to be replaced. Through the years it's deck and hull planking had all been replaced too, so that eventually every single item on the entire ship had been replaced. There was nothing left from the original ship. And yet during all those years and afterwards the sign on the dock still said "This is the ship that fought in the famous battle," and all the parents still brought their children and told them "This is the ship that fought in the famous battle."

Here's the question: Is it actually the same ship or not? Are the parents telling their children the truth or not? If there is not one molecule of material from the original ship remaining because everything has been slowly replaced, should the sign in front of it still say "This is the famous ship," or should it say "This is a replica of the famous ship?"

Which would you say?

If you say that it is the same ship even though all the physical materials have been replaced, then the question becomes: What is it that has persisted throughout all the physical changes? You would perhaps say that the ship's "identity" has persisted, that it is the self-same ship in its "essence," or its soul.

And that is a bit like the question of self, or mind, or identity. In actuality, of course, all the molecules in our bodies are changing all the time. Biologists tell us that all the molecules in our bodies are completely replaced every seven years. So are we the same "self" that we were seven years ago? When we say "I remember when I was nine years old," we are expressing the belief that we are essentially the same self that we were at age nine. We have changed a lot, and have had many new experiences, but we are still essentially the same person. I have the same parents that that nine-year-old had, have some of the same history that that nine-year-old had, etc. We believe we are the same person, but the question then becomes what is the self or mind or soul that has persisted through all the physical changes?

Hume again asks whether this concept of self or mind is a purely theoretical construct which has no basis in actual reality, or if it is an idea based on experience. Hume believes that ideas not based on experience are pure fluff, have no basis in reality, and ought to be thrown out. So is the idea of self based on experience or not? I.e., when we turn inward to experience our own self, or mind, do we actually experience something in there or not?

Hume's conclusion is that when we turn inward what we experience in there are sensations, ideas, perceptions, feelings, etc, but that we do not experience a "mind" or "self" in which those ideas and perceptions reside. Here's the way he says it.

There are some philosophers. who imagine we are every moment intimately conscious of what we call our SELF; that we feel its existence and its continuance in existence; and are certain, beyond the evidence of a demonstration, both of its perfect identity and simplicity.... from what impression cou'd this idea be deriv'd?....

For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception. When my perceptions are remov'd for any time, as by sound sleep; so long am I insensible of myself, and may truly be said not to exist. And were all my perceptions remov'd by death, and cou'd I neither think, nor feel, nor see, nor love, nor hate after the dissolution of my body, I shou'd be entirely annihilated. (A Treatise of Human Nature, Bk I, part vi)

Hume says that since we never have any experience of self, there is no justification for claiming that there is any such thing.

If any one, upon serious and unprejudic'd reflection thinks he has a different notion of himself, I must confess I can reason no longer with him. All I can allow him is, that he may be in the right as well as I, and that we are essentially different in this particular. He may, perhaps, perceive something simple and continu'd, which he calls himself; tho' I am certain there is no such principle in me. ... (A Treatise of Human Nature, Bk I, part vi)

So then what is actually the case, according to Hume. What are we?

I may venture to affirm of the rest of mankind, that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and in a perpetual flux and movement....

They are the successive perceptions only, that constitute the mind; nor have we the most distant notion of the place, where these scenes are represented.

All we are our sensations and perceptions, says Hume. You will recall that Locke believed in four different kinds of existents (things, perceptions, minds, and God) and that Berkeley believed in two different kinds of existents (perceptions and minds, God being an infinite mind). Hume believes in only one kind of existent, namely perceptions. We usually think of perceptions as existing somehow "inside" minds, much like furniture exists inside a living room or beans exist inside a jar. But Hume says that what we have done here is just made up the concept of a mind, or self, so that we would have something for our sensations and perceptions to exist in.

But perhaps a self, or mind, is actually much more like a galaxy than like a living room. A galaxy, as you know, is not a thing inside of which there are stars, planets and other bodies. It is the swirling stars and bodies alone which make up the galaxy. Without the stars and bodies there would be no galaxy. Hume is saying that the same kind of thing is true of minds. A mind is not like a room which has perceptions inside it (even though we may loosely speak as if that were the case). Actually, a mind is nothing more than those perceptions simply swirling around together in a kind of cohesive mass. That is all we are: our swirling and successive perceptions. And "where" all this swirling is taking place, says Hume, is a complete mystery.

If David Hume is correct about these two fundamental concepts on which we base our worldviews, the concepts of cause and effect and self, then much of our human thinking is based on ideas that are purely made up and have no basis in actual experienced fact.

When Immanuel Kant read David Hume and was waked from his "dogmatic slumbers," he began his search for a way to understand the world that could make sense both of Hume's insights and of the ways in which we normally experience the world. The majestic effort that issued out of Kant's struggles took form in his The Critique of Pure Reason, and later in his Prolegomena to Any Future Metaphysic, work that is essential for an understanding of philosophical thought ever afterwards.