Tom Blackstone is the author of Philosophy: What It Is and Why We Need It and a contributing guest writer for CelebrityTypes. As always with guest writers on the site, Blackstone’s piece represents his own insights and not necessarily those of the site.
By Tom Blackstone
David Hume is one of the most influential philosophers of the 18th century, and any professor who teaches a course in Modern Philosophy will expect students to spend some time trying to understand Hume’s ideas.
However, many students who first encounter Hume’s ideas are put off by some of his more extreme statements, such as that we have no “self” that we can be aware of, or that there are no “causes” to events that we can determine. Students often say in response to these ideas that they “just know” that Hume isn’t right, although they admit that they cannot find an error in his arguments. Nevertheless, they often feel some anxiety about his arguments, even if they reject his conclusions.
In addition, Hume’s arguments are so influential in Academia that some students may accept his conclusions simply because they cannot find any significant opposition arguments.
For this reason, I think it’s helpful to not only consider Hume’s ideas in detail, but also to provide the most sophisticated answer to them that I think has yet been offered. In order to do so, I will contrast Hume’s ideas with those of Ayn Rand’s “Objectivist” philosophy.
Historical Background to Hume’s Philosophy
When Hume first came onto the philosophical scene in the late 1700s, European society was changing because of the rise of experimental science. By taking questions that had disputed answers and subjecting them to controlled experiments, scientists were reaching consensus on many issues. Philosophers, on the other hand, were still often debating about the same issues they had been for hundreds of years.
Hume was concerned about this lack of progress in philosophy and wanted to develop a truly scientific theory of human nature. He thought that this would provide philosophy with the respect that it deserved.
Explanation of Hume’s Theory of Definition
Hume begins with a theory of consciousness, or “perception” as he calls it. According to his theory, there are only two types of human perception, or consciousness: “impressions” and “ideas.”
Impressions can be grouped into two categories: “impressions of sensation,” also known as “original impressions”; and “impressions of reflection,” also known as “secondary impressions.” Impressions of sensation consist of sights, sounds, feelings on the skin, tastes, pleasures, and pains. Impressions of reflection consist of emotions and desires.
By contrast with impressions, Hume describes ideas as “faint images of these in thinking and reasoning.” If I look at a lava lamp right now, for example, Hume would say that I experience an impression. But if I remember the lava lamp tomorrow, he would say that I will experience an idea. The idea of the lava lamp in my mind tomorrow will be a faint image of the original impression of the lava lamp that is imposed upon me today.
In addition to this distinction between impressions and ideas, Hume further subdivides both of these categories into “simple” and “complex.” A simple impression or idea contains only one element, whereas a complex impression or idea combines more than one element. For example, if I look at a white square, Hume would say that my impression of the white square is complex, made up of the two simple impressions of white color and square shape. If I remember the white square tomorrow, I will likewise experience a complex idea made up of the simple ideas of white and square.
This theory of perception leads to Hume’s idea of definition. According to Hume, the definition of a word is the idea which the word is connected to. If the word has no idea connected to it, then the word is meaningless. If the word has a complex idea connected to it, then this complex idea should be traced back to its constituent simple ideas. If this cannot be done, then the word is meaningless.
Using this theory of definition, Hume attacks many of the terms that philosophers have traditionally used.
For example, philosophers prior to Hume have always distinguished between our perceptions of the world and the world itself. If a man walks into a room and finds an orange lying on a table, then leaves and returns four hours later to find the orange still there, philosophers have traditionally explained this by saying that there was an orange “in reality” or “in the external world” that was separate from the two experiences that the man had.
However, Hume claims that this use of the term “external world” is meaningless, for two reasons:
- An external world is something that exists apart from our experiences of it. However, we cannot have an experience of something that we do not have any experiences of, as to do so would be a blatant contradiction. Since there is therefore no simple idea attached to the phrase “external world,” the phrase has no meaning.
- An external world is something that continues to exist when it is not perceived. But we cannot perceive something existing when it is not perceived. Once again, there is no simple idea connected to the phrase “external world,” and it is therefore meaningless.
In the past, philosophers have argued with each other about whether we can really know if an external world exists. To Hume, this debate is meaningless because the term “external world” is just meaningless noise. Therefore, he suggests that philosophers should be scientific and stop arguing about a problem that has no answer.
In addition to talking about an “external world,” many philosophers have also talked about an individual “self” that exists apart from any particular experience of it. For example, Descartes argued that although he could doubt the existence of the external world, he could not doubt his own existence, since there would be no one around to do the doubting if he did not exist. Hume disagrees, arguing that when he reflects on his “self,” all he finds is a bundle of perceptions; a succession of sensations, feelings, and urges; that he does not find a single object called a “self” that exists apart from this bundle of perceptions.
Once again, on Hume’s view, the word “self” has no simple ideas connected with it. Like the term “external world” therefore, the notion of the “self” must therefore be meaningless.
Many philosophers in the past have criticized Descartes’ view that we can be immediately aware of our own existence. To Hume, both Descartes and his critics are mistaken because the term “self” has no meaning. Therefore, philosophers should stop arguing about the self altogether.
Hume’s Critique of Causation
Another example in which Hume uses his theory of definition to attack traditional philosophical terms is his consideration of the word “cause.” Philosophers and scientists prior to Hume have usually believed that there is a “law of cause and effect” that operates in the universe and determines how objects behave. For example, if a man fires a pistol at a watermelon from 50 feet, and the watermelon bursts open, philosophers prior to Hume would have explained this event by saying that the shot caused the watermelon to burst open by firing the pistol at it.
Hume disagrees with this way of explaining the event. Hume argues that there are three aspects to causal behavior:
- Spatial contiguity: The bullet and the watermelon are close together in space.
- Temporal contiguity: We see the gun fire, then the watermelon bursts open. These events are close together in time.
- Necessary connection: We imagine that if the gun were to fire again in exactly the same way, with a new watermelon, the new watermelon would burst open.
According to Hume, it is this third aspect of causal behavior, necessary connection, that we have no ground to believe in. Although we do observe some events happening close together in space and time, we do not ever observe any necessary connections between them. Instead, all that we observe is that this time one event followed another. All that we observe is that this time the watermelon exploded after the gun was fired. But that in itself does not give us grounds to believe that the same thing will happen again the next time.
On Hume’s view, there is no simple idea connected to the phrase “necessary connection.” Therefore, like the terms “self” and “external world,” the term “necessary connection” must also be found to be meaningless. And since the term “cause” implies the idea of necessary connection, it too must be meaningless.
Philosophers have wondered in the past how we can know when one thing causes another. Multiple theories have been advanced, but no consensus has been reached. To Hume, the entire debate is ridiculous, since the philosophical word “cause” is meaningless. Philosophers should therefore stop wasting their time.
Hume’s Ethical Theory
To provide one final example by which Hume attacks traditional philosophical concepts using his theory of definition, we can consider his idea of Ethics. Traditional philosophers, such as Aristotle and Plato, have argued that Ethics is a product of reason. According to them, human beings have a choice to do what is rational and good or to do what is irrational, self-destructive, and evil.
For Hume, Ethics can never be a product of reason because reason cannot be used to derive what ought to be, as opposed to what is. We cannot see, taste, touch, hear, or smell “goodnesss.” Therefore, when a man says “it is good not to rob people” he simply means that it is desirable to him that someone else not rob people. Ethics is therefore a product of feelings, customs, and habits – but not reason.
In Hume’s view, in order for Ethics to be derived from reason, there would have to be a simple idea connected to the idea of “goodness.” However, there obviously is not. We cannot trace terms like “should,” “ought to,” “desirable,” or “good to do,” back to anything that we can see, taste, touch, hear, or smell. These terms therefore, are meaningless when used for any reason other than to say that we simply desire something.
Throughout history, philosophers have argued over what constitutes the good life. No consensus has emerged. In Hume’s view, the term “goodness,” as philosophers have traditionally used it, is again meaningless. Philosophers should therefore also stop arguing about ethics.
The Objectivist Response to David Hume
At the time that Ayn Rand began writing, philosophy was split into two camps. On the one side were the analytic philosophers who agreed with David Hume that both questions about the nature of reality and about ethics were meaningless. These philosophers wanted to be “scientific” by asking questions that could be answered through logic and the study of language. On the other side were the continental philosophers who believed that philosophy should be practical and should therefore answer questions about the nature of reality and the good life. However, these latter philosophers also agreed with Hume that such questions could not be answered through reason. Therefore, they advocated “irrational” means such as poetry and storytelling to answer these questions. However, both sides agreed that traditional philosophical questions could not be answered through reason.
Rand was deeply concerned about this anti-rationalistic trend in philosophy and believed that it was responsible for a moral decay that had taken over Western Civilization. In her view, the rise of totalitarian systems of government in Russia, Germany, and Italy provided significant evidence for this decay. Rand believed that humanity was abandoning the Ancient Greek belief in rationality and virtue, and that society was in danger of collapsing as a result.
Rand wanted to restore traditional philosophy as the foundation of morality, and therefore to give it a place of reverence in the world.
Rand’s Response to Hume
Rand begins her account of consciousness by dividing it into three stages: Sensation, perception, and conception. Sensation is an automatic reaction of a sense organ from the outside world. Perception is a group of sensations retained by a living organism and integrated by its brain into an awareness of “entities,” or “things.” Conception is a “mental integration of two or more concretes … isolated by a process of abstraction and united by means of a specific definition.”
For Rand, the process of forming concepts is “volitional.” It is something that we must choose to do. Nature will not impose concepts upon our minds. In addition, forming concepts correctly is not easy to do. In order to make sure that our concepts are valid, we must find the distinguishing characteristic that sets the members of the concept apart from other objects that are not included. For example, in order to correctly form the concept “animal,” we must realize that our siblings and pets are included in this concept but not our Mom’s plant that is sitting out on the front porch.
Unlike Hume, Rand does not equate concepts with “ideas” that are faded memories of impressions. Instead, she uses this term to denote a group of objects viewed as belonging together, such as “human being,” “car,” “tree,” “building,” etc.
Again unlike Hume, Rand also distinguishes sensations from perceptions. In Rand’s view, a white square is not a “complex impression” that can be broken down into simple impressions. Instead, it is an “entity”; a complete thing perceived by us as a whole. Although we can speculate philosophically that there must have been a time when this white square would have appeared simply as a blob of color and shape (i.e. as a sensation), this is a conceptual discovery that should be not be used to attack the very validity of perception itself.
Perception, for Rand, is not volitional. We cannot choose to see the elements of the white square as separate from each other. The white square simply appears to us as an indivisible unit. Therefore, perception cannot be “invalid,” because the concept of “invalidity” only applies to volitional processes. According to Rand, we cannot make mistakes about things that we cannot control. Therefore, we cannot use an invalid method (make mistakes in which method we use) when only one method is open to us.
Hume had said that the concept of an “external world” is meaningless. But for Rand, we perceive an “external world” every time that we look at it. Right now, writing this piece, I perceive a computer screen, and a keyboard. An hour ago, I perceived a television in my living room. In each of these cases, I perceived an “external world.” Through concepts, I can abstract away my own perception from the thing itself. I can realize that my perception of the television today is separate from my perception of it yesterday, and that the television set is itself separate from each of my experiences. But recognizing this requires that I operate at the conceptual level of consciousness. In perception, I simply see the television. It does not appear to me to be a “simple impression.” On the contrary, it appears to be a television; something which is obviously separate from me.
What is true of the television is true of the external world in general. For Rand, when Hume argues that the notion of an “external world” is impossible (because you cannot perceive something that you don’t perceive), he is confusing the perceptual and conceptual levels of consciousness. We must first perceive the external world. Only by thinking about what is happening can we then realize that we are perceiving it, and that this perception is separate from the thing perceived. In order for Hume to validly say that we are unreasonable for believing in an external world, he would have to prove that conceptualization itself is invalid. However, he assumes this rather than proving it.
Rand’s Criticism of Hume’s No-Self View
Rand also disputed Hume’s assertion that human beings don’t really have a “self,” but only a bundle of internal perceptions. According to Rand, we do not perceive ourselves as a “bundle of impressions.” We perceive ourselves as a unity. In fact, Rand turns Hume on his head and says that it is only through abstraction that we achieve an understanding that within the self there is a continuous stream of thoughts and feelings.
Rand’s Criticism of Hume’s Critique of Causality
Rand’s criticism of Hume’s view of causality is similar to the previous two lines of criticisms: In Rand’s view, we can see necessary connections (the very thing that Hume had denied) directly: For example, suppose I have a feeling that I want to lift a glass, and I both feel and see myself lifting it. I do not perceive this as “spatial contiguity” or “temporal contiguity,” with “necessary connections left out.” On the contrary, the entire action is experienced by me as one continuous process which I brought about. In the same way, when I see a man fire a gun into a watermelon, the entire process appears to be a continuous, causally connected action.
The “law of causality,” i.e. the rule that every effect must have a cause, is an abstract, conceptual realization. It comes from observing many different events in many different circumstances and then thinking about what has occurred. It comes from the realization that things are what they are and must behave the way that they behave. But the fact that this law is a piece of conceptual knowledge does not invalidate it on that account alone.
Rand’s Criticism of Hume’s Ethics
In regards to Ethics, Rand argues that values or “things that one should do” arise in the context of life. Unlike inanimate matter, living things can cease to exist. If a fish does not swim fast enough to avoid being eaten, the matter that composed it will remain in the stomach of the organism that ate it, but its life will go out of existence. In order to continue to exist, organisms must constantly work to preserve their lives.
Human beings, however, have a peculiar problem that other organisms do not have. While other organisms automatically pursue what is best for them, human beings do not. The reason they do not is because human beings can only survive by conceptualizing, and conceptualization is volitional.
In regards to the argument that our senses do not tell us what we ought to do, but only what we actually do, Rand responds by saying that what a thing is determines what it ought to do and that we can identify what we are through the conceptual identification of our perceptions. For example, we can identify perceptually which things make us feel pleasure and which make us feel pain. On the conceptual level, we can then determine that things usually cause us pain because they threaten us and that things usually cause us pleasure because they preserve us. On a greater level of abstraction, we can come to understand that our emotions of joy and sorrow are conceptual equivalents of the basic pain/pleasure mechanism and that we can program this mechanism to lead us to the things which are the best for our lives. For example, we can initiate an exercise program even though it causes us pain, and can even come to feel joy while using this program because of the knowledge that it is making us healthier. On an even greater level of abstraction, we can come to understand The Randian Virtues: Rationality, Productiveness, Pride, Honesty, Integrity, Independence, Justice, and that the consistent practice of these virtues will lead to a successful and happy life.
These are only some of the principles of Rand’s philosophy, the ones that I thought were most relevant to rebutting the claims of David Hume. Hopefully, these arguments are enough to dispel any anxiety that a student may feel when hearing that “there is no self” or “there is no external world.” Or, if a student finds Hume’s arguments convincing, hopefully this is enough to cause that person to question Hume’s conclusions.
 Hume: A Treatise of Human Nature §1.1.1
 Rand: The Objectivist Ethics §36
Image of Hume in the article commissioned for this publication from artist Georgios Magkakis.