The Nature of Substance


The Nature of Substance, Reality, and Mind: Idealism, Dualism, and Materialism

There are a number of complex philosophical issues brought about by a discussion of substance. As you may recall from an earlier chapter, the Ancient Greeks were very much concerned about the question of substance. At present, science tells us everything is made up of material atoms, and yet, philosophers still debate this scientific conclusion. It is not to say that atoms do not exist (although no one has actually seen one, which is another question about scientific realism), but rather a question of what is reality made up of, mind, matter, or a combination of both.

These questions lead to other questions regarding the nature of the human mind. Is it just the brain or does it have an immaterial component? What of the soul? All these questions will be considered in the following sections below.


Materialism claims that all real objects are physical. Dualism claims that all real objects are either physical or nonphysical. Idealism claims that all real objects are nonphysical.

Berkeley and Idealism

Berkeley contends that the only things that are real are ideas. This view is known as idealism. All the objects we encounter in the world (which is an idea as well) are nonmaterial objects. As bizarre as this may at first sound, what you should be aware of is the fact that the only objects that we do have direct access to in our mind (or brain) are ideas.

We assume that our idea of objects in the world is tied to or come from these objects; some underlying physical substance, yet Berkeley is denying that we have any good reason to infer to this material substance. Berkeley employs a radical empiricism. He thought that we can only acquire knowledge from our experiences—from our per- ceptions. What is the nature of our perceptions? We assume that we perceive objects directly, yet in fact, what we are doing is experience an idea of the object, which has been constructed by our mind. Berkeley goes on to argue that “to exist is to be perceived.”

Berkeley contends that the only things that are real are ideas. All the objects we encounter in the world—which is an idea as well—are nonmaterial objects. As bizarre as this may at first sound, what you should be aware of is the fact that the only objects that we do have direct access to are our ideas. We assume that our idea of objects in the world are tied to or come from those objects (we think those ideas correspond to object in reality), some underlying physical substance, yet Berkeley is denying that we have any good reason to infer to is this material substance.

He may have a point. Consider a strawberry, for example. It has a certain color, shape, and weight; it has a particular texture, taste, and smell. These are all perceptions, ideas in your mind. If you take away the taste of the strawberry, take away its smell, its weight, its shape—what do you have left? Nothing. The strawberry is a bundle of those perceptions. Reality is a bundle of perceptions. In fact, Berkeley

believed, “to be is to be perceived”: esse est percipi. To take another example, consider an object, such as a desk in a room. What do you see besides color, shape, and exten- sion? If all we perceive are these things, and these qualities are ideas in the mind, why posit the existence of some other substance, matter that is unperceived? Berkeley goes on to make a distinction between immediate and mediate objects. Immediate objects are those we perceive directly, while mediate objects are those that we infer from our immediate perceptions.

In his view, matter or substance is something that we infer exists, but, in fact, we do not directly perceive. Yet what would the matter be like. What would the noumenal world (of Immanuel Kant (1724–1804, to be discussed later) be like? Is it not something that we can never know, yet we posit or assume that it exists? What Berkeley says is that we don’t need material substance to explain our experiences, and it is an unwarranted inference to draw because there is no reason to assume that our ideas that are of the phenomenal world correspond to a physical or material reality.

Berkeley goes on to mark a distinction in the type of minds that exist. He states that the world is composed of two things: ideas and minds. To be an idea, it must be perceived. Perceived by what? A mind. A mind is a perceiving thing. Finite minds can only perceive a limited number of ideas, so what happens to this room when no one is here to perceive it? Does it cease to exist? If that were the case, then how come it always reappears when some perceives it? Would it be the same room?

“If a tree were to fall on an island where there were no human beings would there be any sound?”

—The Chautauquan Magazine, 1883, in discussion of Berkeley’s metaphysics

Objects continue to endure, according to Berkeley, because there is one, Infinite Mind. His answer is that it the world continues to endure when we do not perceive it because it continues to be perceived by the infinite mind—God. God is an infinite mind that perceives all things. Ultimately, his entire philosophy can be boiled down to this one profound thought: to exist is to be an idea in the mind of God.

Powerful Thinkers: Immanuel Kant

One of the most influential philosophers in history, Immanuel Kant was born on April 22, 1724, in Königsberg, Prussia. He died there in 1804, never having strayed far from home and having lived a rela- tively quiet life. Yet, this quiet, lifelong bachelor’s works transformed philosophy forever.

Kant, in his monumental (and monumentally difficult) Critique of Pure Reason (1781) questioned the necessary conditions of experience, and he explored our possibilities of knowledge. He drew a distinction

between phenomena, the reality of appearances in our everyday life as we live it, and noumena, realities that exist independent of the human mind’s interpretation. Kant analyzed human experience and the way we organize it in terms of how that reality appears to us phe- nomenologically but also how it really is—a radically precise reas- sessment of a problem that goes back to Plato and Aristotle. Kant’s transcendental idealism explains how humans interpret the world by imposing structures and order on our perceptions of that world.

The human mind organizes experience based on categories we impose on experience. A priori propositions, such as 2 + 2 = 4, do not depend on experience. A posteriori propositions rely on experience for justification. For example, the proposition “Sally is hungry” relies on experience to show whether or not it is true.

Kant’s contributions to ethics, was as least as influential as his meta- physics. He began with his search for one ultimate principle to guide morals in 1785 Groundwork for the Metaphysics of Morals and contin- ued as he explained the rational justification for ethical judgments in his 1788 The Critique of Practical Reason. In 1790, The Critique of Judg- ment followed. For Kant, reason is the guiding principle of morals. This principle was his categorical imperative, a product of reason that states simply that you should act always as if according to a maxim that you would turn willingly into a universal law and also that you should always treat humanity—in your own person as well as that of others—as an end in itself and never as a means to an end. Kant’s ethics is discussed later in this book in the chapter on ethics.

Kant led a quiet life, and he stuck to his daily constitutional walking schedule so consistently that, so the story goes, housewives in Königs- berg would set their clocks by him. He began lecturing at the Univer- sity of Königsberg in 1755, finally got tenure as professor of logic and metaphysics in 1770, and soon afterwards wrote his first Critique.

The only controversy that came his way was when he wrote in his first his first Critique that “our age is an age of criticism, and to criticism all our beliefs must submit. Religion in all its holiness, and the state in its majesty, cannot exempt themselves from its tribunal without arous- ing suspicion against themselves.” Kant thought that the question of God could not be answered rationally, an insight not welcomed in conservative Prussia. The King of Prussia in 1792 forbade Kant to his lecture or writing on religion. He continued teaching in Königsberg until he retired in 1796, shortly after the publication of his visionary 1795 political work Perpetual Peace.

René Descartes and Substance Dualism

René Descartes (1596–1650) holds a view known as substance dualism or simply dualism. He maintains that reality is composed of two substances: mind and body. Mind is immaterial essence and body is material essence. All our thoughts and feelings are immaterial and exist in our mind, whereas our body exists in mate- rial space. He held that these two substances, one material and the other immaterial, interact with each other at some point in the body.


René Descartes gives a number of arguments in an effort to try to prove the mind is not the body. Here are two such arguments:

I can doubt my body

1) I can doubt my body

2) I cannot doubt my mind

3) Since the mind and body have different properties, they must be dis- tinct objects

4) Therefore, my mind and body must be distinct things

From the above argument, Descartes concludes that the mind and body must be different objects. The problem with the above argument is that Descartes’ doubt is not an actual property of his body or of his mind—it

had no bearing on their existence or nonexistence. Perhaps seeing this flaw, he developed the following argument.

My mind and body have different properties

1) Body is physical

2) Mind is not physical

3) Since the mind and body have different properties, they must be distinct objects

4) Therefore, my mind and body must be distinct things

Physicality is an actual property of objects, so this argument avoids the flaws of the one discussed above. Unfortunately, the materialist will deny premise 2, whereas the idealist will deny the truth of premise 1—this leaves us where we started—unfortunately.

Other Views on the Interaction of Mind and Body

There are various other views on the nature and connection between the mind and the body. Identity thesis states that the mind and brain are identical. Dualism as noted above claims that the mind is mental and distinct from the brain is physical. Parallelism, which is also known as Epiphenomenalism, claims that what happens in the mind also happens at the same time in the brain, but there is no con- nection between the two things. Finally, Occasionalism, which is a version of epi- phenomenalism, states that although there is no connection between the mind and brain, magically or supernaturally God makes the two interact—so that when I think of something mentally, my body will follow my thoughts or vice versa.

John Searle—Supervenience

John Searle (b.1932) holds a version of dualism known as supervenience theory. At times, he claims it is dualism, and at other times, he claims, it is not. Most philoso- phers, against his objections, agree that his theory is a version of dualism but, let him call it what he wants. “The history of the philosophy of mind over the past hundred years,” Searle wrote, “has been in large part an attempt to get rid of the mental by showing that no mental phenomena exist over and above the physical.”

Whereas Descartes is willing to admit that the mental and physical are two dif- ferent substances (and hence this theory is technically known as substance dualism), Searle is unwilling to make that claims; though he thinks there is a men- tal and a physical, they may be two aspects of a single substance (not unlike Baruch Spinoza (1632–1677)) . He claims that consciousness (the mental thing going on in your head) comes from or supervenes upon the physical—in this case, the brain. The mental plays a causal role in explaining behavior and in our actions. The men- tal may not be immaterial, but it still exists.

This view, along with Berkeley’s idealism, and Descartes’ substance dualism can make sense of the notion that our thoughts, feelings, and intentions exist, but they are not the same as material objects.

Thomas Hobbes and David Armstrong

According to Thomas Hobbes (1588–1679), the only things that exist are “bodies [objects] in motion.” It is his view that thoughts, ideas, and feelings are physical entities explained by motions in the brain. Writing in the 1600s, he had no notion of neurons or any deep understanding of the human brain, yet he was certain all of these so- called mental properties would reduce to something physical taking place in the brain.

David Armstrong (1926–2014) argues for a strong version of materialism just as Thomas Hobbes does. Armstrong’s materialism holds that there is only one sub- stance, and it is material. Whatever consciousness is, it is material. The only things that exist are physical objects. As he says in his book, The Nature of Mind and Other Essays (1980), the mind “is not something behind the behavior of the body, it [is] simply part of that physical behavior.”

Contemporary Theories of Philosophy of Mind

There are a number of contemporary interpretations of what is collectively known as the mind/body problem. Reductionism is the view that the mind will be reduced to the body. It claims that neuroscience will one day reduce the mental to physical objects such as neurons. Identity theory claims that the mind is identical with the brain. Functionalism claims that the mind is identical with any object that functions like a brain.

Powerful Thinkers: Alan Turing

Can a computer think? Does it have a mind? Asking whether a machine could be taught to imitate the behavior of humans is the main question behind artificial intelligence, and the answer to that question is one of the many contributions of Alan Turing (1912–1954), the visionary mathematician and philosopher of sci- ence whose discoveries are the foundation of today’s artificial intelli- gence and computer science. If you study the philosophy of mind or the relation of the mind to mathematics; if you just use a smart- phone, a mainframe, or a laptop; if you store information on a cloud; or even if you’ve seen the 2014 film The Imitation Game, you’ve been touched by the thoughts of this genius.

His tale is as extraordinary as it is tragic. Turing studied quantum mechanics, probability theory, and logic at Cambridge and then at Princeton, returning to England in 1939 to offer himself to the war effort. His individual contribution to victory in World War II has been ranked with those of Winston Churchill and Dwight D. Eisenhower— and that is no exaggeration. It was Turing’s cryptanalyses at Bletchley Park that led to breaking the Nazi Enigma code, giving the Allies the necessary information to counter U-boat attacks and save the Battle of the Atlantic. Turing’s discoveries saved thousands of lives, but the details of his highly classified secret work did not become public until 2012.

The imitation game Turing devised is an original vision of a computer hardware that could store information and change functions according to the task at hand, so that it did not need to be recali- brated for each computation. In other words, he invented hardware that could imitate the way a person thinks, except the Turing machine could do it much, much faster. In his now famous essay Computing Machinery and Intelligence, Turing first asked the question “Can machines think?” setting up a challenge to epistemology and philosophy of mind that goes on to this day.

If consciousness is physical, as materialists believe, then there is no reason why it could not be imitated by a computer—which then could be said to be thinking. The problem with human conscious- ness, however, is that we in fact have no evidence showing that the mind is indeed made of matter, in this case the brain, than we do that it is not. As Tom Stoppard has the neuroscientist Hilary say near the end of his 2015 play The Hard Problem, “when you come right down to it, the body is made of things. And things don’t think.” That is indeed the hard problem, one we may never solve.

After World War II, Turing continued his research on programming, neural nets, and the budding field of artificial intelligence, while working at the National Physical Laboratory in London. He proposed the first mathematical use of a computer and developed a Turing test for machine intelligence. He began groundbreaking research into the mathematical basis of life and developed a theory of nonlinear biological growth.

The war hero was gay, however, at a time when homosexuality was illegal in England. He was arrested, lost his security clearance, fired, jailed, and sentenced to chemical castration in 1952. He committed suicide in 1954.

Alan Turing received a posthumous royal pardon from Her Majesty Queen Elizabeth II in 2013 on Christmas Eve. Following the pardon and the renewed public gratitude to this powerful thinker who helped the Allies win the war, there is presently a movement to pardon the other 50,000 gay men who were convicted under England’s antigay laws.


Can a computer have a mind or a soul?

Logical Behaviorism

Gilbert Ryle (1900–1976) holds a view of the mind known as logical behaviorism. This view claims that behavior can be explained without positing the existence of a mental realm. Under this conception, it is not logically necessary to discuss the men- tal when speaking about behavior. He uses the example of the ghost in the machine. This example is that someone might think that a ghost is responsible for the workings of a machine, but there is a different explanation, simply the physical construction of the machine—if you were to examine all of the parts together, you discover that the machine has a completely mechanical explanation for its operations. For example, if you showed a television or tablet PC to some primitive tribesmen, he might think it was magic or had a spirit inside of it, but in fact it is just electronics, circuits, and com- puter chips—no magic is required. The same may be true of the brain. We think the mind is this magical thing, when it is simply the workings of the brain.

Personal Identity and Artificial Intelligence

David Hume (1711–1776) claims that the self is an illusion and that we can never, in any of our experiences, find a perception of the actual self. In his view, the self is constantly changing and you are never the same person one moment to the next. This view is not unlike some Eastern conceptions of the self and of the mind. It is also close to Jean-Paul Sartre’s notion that human beings are nothingness, that is, not-a-thing, and as such cannot be defined. There is no ego, there is no self. Accord- ing to Hume, all knowledge is based on sense impressions and on experiences. If this is the case, we don’t even have any evidence of the self, since any conception of iden- tity must be based on impressions. “It must be some impression that gives rise to every real idea,” he wrote in his Treatise on Human Nature. “The self is not any one impression, but that to which our several impressions are supposed to have a refer- ence.” There is no self. Therefore, as far as our idea of the self, Hume believed “there is no such idea.”

Although Hume argues against the self, other philosophers have argued for the existence of the self. Thomas Reid (1710–1796) argues that the mental ability of memory gives us reason to hold that the self exist. Daniel Dennett (1942) claims that a fundamental principle of evolution is self preservation as such the self must exist. The debate is not new, but recent scientific developments have made it more of a burning issue. If the self, the human mind, is a complex physical instrument—purely

“Listen carefully; what characterizes the mind is clinging to the notion of a self. But if one looks carefully into this ‘mind’, one actually sees no self at all. If you can learn how really to observe this [apparent] ‘nothing’, then you’ll find that “something” will be seen”

—Jetsun Milarepa, 1052–1135, The 100,000 Songs of Milarepa

Although Hume argues against the self, other philosophers have argued for the existence of the self. Thomas Reid (1710–1796) argues that the mental ability of memory gives us reason to hold that the self exist. Daniel Dennett (1942) claims that a fundamental principle of evolution is self preservation as such the self must exist. The debate is not new, but recent scientific developments have made it more of a burning issue. If the self, the human mind, is a complex physical instrument—purely

material, as most neuroscientists believe—then it is not only possible but probable that we will eventually explain everything there is to know about the self by studying how the brain works. And it is also possible and probable that a computer system will do that as well.


Can we know the self, or is the self simple like an empty theater as Hume proclaims?

Materialism is the rule in the science, and that position permeates much phi- losophy as well; it is certainly an easier proposition to say that all there is, is matter— and thinking is just part of a physical process. Although most people are very likely dualists—anyone who believes in God must be, for example, since God is not mate- rial—including atheists such as Jean-Paul Sartre who are not materialists and then have a tough time explaining what the mind is. Still, such an explanation is needed if we are to insist that a computer cannot “think” the way humans can.

That possibility is here, stemming from Alan Turing’s original work on artifi- cial intelligence and since then taking off at an exponential rate of success. Computers today not only do what only humans used to do, but they do so faster and more accurately. Does that make them intelligent? Does it mean that computers think? Maybe? In 1962, Time Magazine named The Computer its “Man of the Year.” And that was just the beginning.

On film at least, of course. The vengeful computer HAL in Stanley Kubrick’s 2001: A Space Odyssey (1968) got the ball rolling in frighteningly believable sci-fi movie, followed by an invasion of smart androids in Ridley Scott’s Bladerunner (1982), an adorable and tragic little boy robot in Steven Spielberg’s A.I. (2001), or a sexy dis- embodied voice online who dumps a real guy for a smarter artificial intelligence in Spike Jonze’s Her (2013), to name a few of the best.

But there’s no need to go to sci-fi movies, just grab your phone. The impres- sively complex technology involved in designing that computational machine would have been unthinkable only a few decades ago. Maybe computers do think. Still, does the chess program on your laptop feel good when it beats you in every game? Does it judge the music you put on the iCloud? Is your computer punishing you when it freezes? Is it sad when it gets a virus? Does it like chicken soup?

Apple’s intelligent personal assistant iOS app Siri, the voice that talks to you in your car or phone, certainly seems intelligent. Siri uses a sophisticated system to interface with your own voice, gets to know you in the sense that her answers—part of the design of her software—will adapt to you the more you ask her. You can ask her “Siri, where is nearest beach?” or “Siri, what is neurophysiology?” But the smartest of smartphones, even with the latest iOS Siri app, is likely to answer your question “Siri, how can I be happy?” with something like “Macy’s is on 34th Street.” You are not talking the same language. Or, what is more likely, you are conscious and self-conscious, and Siri is not.

Some scientists would say that your own happiness and sadness in fact are not that different from the computer’s, as long as what you mean by emotions is precisely whatever goes on in your brain and whatever behavior you perform when you feel those emotions. That is a materialist view, and we do know a lot about matter. The presumption on part here is to assume that our knowing everything there is to know about physical reality leads us to know everything there is to know about the mind. It is fact a popular trend in Anglo-American analytic philosophy to assume just that. The self can or will be explained and understood in physical terms. It’s all about the nerve cells and what they do in that complex gray matter called your brain. Any- thing else is in the realm of mysticism, of returning to Plato, or—God forbid—of psychology. That is, as Tom Stoppard puts it, the hard problem.

And the problem is there, still. To doubt the materialist view of the self is not to doubt science: much of science is as verifiable as 2 + 2 = 4. Evolution is true, for example. The Big Bang Theory is true, as is the Law of Gravity. The Earth is billions of years old. Intelligent design theory of creation is not so intelligent. The idea is not to ask questions that were answered already and bring about confusion and retro- gression, but rather to avoid trusting answers for which there is no foundational evi- dence. A scientific theory of consciousness is easy, but only if you assume that physics, biology, and chemistry are the way to explain the mind. Yet materialism is a premise, not a conclusion.

We have evidence of dualism, hard as it is to prove it. Kurt Go ̋del upset many philosophers and mathematicians when he proved that there are true facts that cannot be proved but are nevertheless true. The tough part is explaining them.


RENÉ DESCARTES: Meditations on First Philosophy

Searching for a truth that is clear and distinct, René Descartes sets off on a journey of radical doubt that leads to one certain fact he cannot doubt: that he is thinking.

Meditation 1

12. I will suppose, then, not that Deity, who is sovereignty good and the fountain of truth, but that some malignant demon, who is at once exceed- ingly potent and deceitful, has employed all his artifice to deceive me; I will suppose that the sky, the air, the earth, colors, figures, sounds, and all exter- nal things, are nothing better than the illusions of dreams, by means of which this being has laid snares for my credulity; I will consider my-self as without hands, eyes, flesh, blood, or any of the senses, and as falsely believ- ing that I am possessed of these; I will continue resolutely fixed in this belief, and if indeed by this means it be not in my power to arrive at the knowledge of truth, I shall at least do what is in my power, viz., [ suspend my judgment ], and guard with settled purpose against giving my assent to what is false, and being imposed upon by this deceiver, whatever be his power and artifice.

Meditation 2

1. The Meditation of yesterday has filled my mind with so many doubts, that it is no longer in my power to forget them. Nor do I see, meanwhile, any prin- ciple on which they can be resolved; and, just as if I had fallen all of a sudden into very deep water, I am so greatly disconcerted as to be unable either to plant my feet firmly on the bottom or sustain myself by swimming on the surface. I will, nevertheless, make an effort, and try anew the same path on which I had entered yesterday, that is, proceed by casting aside all that admits of the slightest doubt, not less than if I had discovered it to be abso- lutely false; and I will continue always in this track until I shall find something that is certain, or at least, if I can do nothing more, until I shall know with certainty that there is nothing certain. Archimedes, that he might transport the entire globe from the place it occupied to another, demanded only a point that was firm and immovable; so, also, I shall be entitled to entertain the highest expectations, if I am fortunate enough to discover only one thing that is certain and indubitable.

2. I suppose, accordingly, that all the things which I see are false (ficti- tious); I believe that none of those objects which my fallacious memory rep- resents ever existed; I suppose that I possess no senses; I believe that body, figure, extension, motion, and place are merely fictions of my mind. What is there, then, that can be esteemed true ? Perhaps this only, that there is abso- lutely nothing certain.

3. But how do I know that there is not something different altogether from the objects I have now enumerated, of which it is impossible to enter- tain the slightest doubt? Is there not a God, or some being, by whatever name I may designate him, who causes these thoughts to arise in my mind ? But why suppose such a being, for it may be I myself am capable of pro- ducing them? Am I, then, at least not something? But I before denied that I possessed senses or a body; I hesitate, however, for what follows from that? Am I so dependent on the body and the senses that without these I cannot exist? But I had the persuasion that there was absolutely nothing in the world, that there was no sky and no earth, neither minds nor bodies; was I not, therefore, at the same time, persuaded that I did not exist? Far from it; I assuredly existed, since I was persuaded. But there is I know not what being, who is possessed at once of the highest power and the deepest cun- ning, who is constantly employing all his ingenuity in deceiving me. Doubtless, then, I exist, since I am deceived; and, let him deceive me as he may, he can never bring it about that I am nothing, so long as I shall be conscious that I am something. So that it must, in fine, be maintained, all things being maturely and carefully considered, that this proposition (pro- nunciatum ) I am, I exist, is necessarily true each time it is expressed by me, or conceived in my mind.

4. But I do not yet know with sufficient clearness what I am, though assured that I am; and hence, in the next place, I must take care, lest per- chance I inconsiderately substitute some other object in room of what is properly myself, and thus wander from truth, even in that knowledge (cog- nition) which I hold to be of all others the most certain and evident. For this reason, I will now consider anew what I formerly believed myself to be, before I entered on the present train of thought; and of my previous opinion I will retrench all that can in the least be invalidated by the grounds of doubt I have adduced, in order that there may at length remain nothing but what is certain and indubitable.