David Bruce (born 1954): Metaphysical Theories’ Strengths and Weaknesses


David Bruce

One good way to choose among competing metaphysical theories is to list their strengths and weaknesses, then choose on that basis.


Materialism is the view that all reality consists of matter. Thus, the only things that are real are empty space, physical (that is, material) objects, and energy. Epicurus is a Materialist.


One strength of Materialism is that it is the view presupposed by modern science. Scientists assume that there is a cause for everything that happens. In addition, scientists assume that the cause naturally occurs in the universe. Thus, if we get ill, scientists look for a reason why we became ill; for example, a virus or a cancer. Obviously, science has been very successful — we owe many wonderful inventions to scientists. However, scientists — in investigating the universe — assume that transcendental entities such as God or minds don’t exist. (Of course, some scientists believe in God, but they would agree that to say “a miracle occurred” is a poor explanation of the results of an experiment.)

Another strength of Materialism is that most of us assume that an external physical world exists. We are accustomed to speak of physical objects as opposed to the objects we only dream about. Materialism does a good job of explaining physical phenomena.


A weakness of Materialism is that it does a poor job of explaining mental phenomena such as wanting, thinking, dreaming, etc. After all, there is a difference in the way that I feel something and in the way that I observe you feel something. When I have an earache, I really feel it. When you have an earache, I see you hold your hand on your ear and I hear you moan, but I don’t feel the earache. Why is there is a difference in the pain I experience and in the pain I observe you experiencing? After all, according to the Materialists, the only thing that exists is matter and both of us are physical objects. How can something that is only physical experience pain or a dream, or make a wish?

Another weakness of Materialism is that it pretty much shuts the door on the idea of our being immortal. After all, we know what happens to our body after we die — it decays. I suppose that a god could reassemble our scattered atoms and bring us to life again, but then that kind of god would transcend matter and according to Materialism, no such transcendent being exists. (In the Christian religion, St. Paul believed that we would be resurrected; in the afterlife, each of us will have what he called a spiritual body.)


Idealism is the view that all reality consists of minds and ideas. Objects are not physical; instead, they are bundles of ideas that are perceived by minds. George Berkeley is an Idealist.


A strength of Idealism is that it does a good job of explaining mental phenomena such as wanting, thinking, dreaming, etc. After all, we are minds and everything that exists is a bundle of ideas that we perceive. Of course, Idealists can account for wanting, thinking, dreaming, etc.

Another strength of Idealism is that it is possible that we are immortal. Perhaps our mind will live on although the bundle of ideas we call our body disintegrates.


A weakness of Idealism is that we need to ask how objects stay in existence when they are not perceived. After all, according to George Berkeley, to be is to be perceived. Therefore, if no one is in my office to perceive the office furniture, does that mean that the office furniture ceases to exist? Berkeley came up with the theory that God perceives everything; therefore, everything stays in existence even when no one is around to see it.

Another problem with Idealism is that it finds it difficult to account for our knowledge of our own minds. David Hume, who was an empiricist, believed that all that is perceived by us is a flow of sensations, thoughts, and memories, but that a mental substance called a mind is not perceived by us. Therefore, why should we believe that we have a mind that is a mental substance? Berkeley criticized belief in material substance, but Hume used the same kind of arguments to criticize belief in mental substance.


Dualism is the view that all reality consists of both minds and bodies. Therefore, a human being has a body but also has a mind or soul. Both René Descartes and Plato are Dualists.


A strength of Dualism is that, as Richard Taylor points out, it avoids the problems of the Identity Theory (the Materialist theory that we are identical with our body). One problem with the Identity Theory is that we can’t say the same things about our mind and body. For example, we can say “my mind has a wish,” but it is absurd to say “my body has a wish.” Or we can say, “I am religious,” but it is absurd to say, “my body is religious.”

Also, in our minds we sometimes make mistakes. In the second edition of his book titled Metaphysics, Richard Taylor uses the example of thinking that today is February 31, and then asks:

“Now how can a physical state of any physical object be identical with that? And how, in particular, can anything be a false physical state of an object? The physical states of things, it would seem, just are, and one cannot even think of anything that could ever distinguish one such state from another as being either true or false. A physiologist might give a complete physical description of a brain and nervous system at a particular time, but he could never distinguish some of those states as true and the others as false, nor would he have any idea what to look for if he were asked to do this. At least, so it would certainly seem.”

Another strength of Dualism is that we experience so much of the world in terms of having a mind and a body. They are concepts that we are comfortable with and use in our language.

A third strength of Dualism is that it is possible we are immortal: Our mind may survive the deaths of our body.


The major weakness of Dualism is the mind-body problem. If we are both mind and body, then how do our mind and body interact? After all, the body is material, while the mind is immaterial, so how can one affect the other? If I try to use my mind to move an object such as a pencil off the floor, the pencil won’t budge until I lean down and pick it up with my fingers. How can my mind tell my body to move? And how can my body interact with my mind?

A weakness with Dualism is stating how the mind is related to the body. “Possession” is a social and legal term, so we can’t say that the mind possesses the body. In addition, “occupy” is a physical term, so we can’t say that the mind occupies the body.


I leave it up to the reader to decide whether Materialism, Idealism, or Dualism is the correct metaphysical theory.


Copyright by Bruce D. Bruce; All Rights Reserved


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