Idealism: the Arguments

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This is the the sixth post in my Theories of Knowledge and Reality series. Follow the link for more on the series and for links to other entries as they appear.

(Note: My presentation of these issues is heavily influenced by Peter van Inwagen's chapter on idealism in his Metaphysics.)

In the last post, I explained the idealist view of George Berkeley. In this post. I'll look at two arguments he gave in favor of that view and one argument against it.

One of Berkeley's primary reason for holding this view had to do with what he saw as a contradiction in the view that there are external objects. One way to reformulate his argument that I think is a little more intuitive is as follows:

A. The whiteness is a property of the paper.
B. The whiteness is a property of an idea (in my mind) of the paper.
C. Therefore, since the whiteness is a property of one thing, the paper must be just an idea (in my mind).

The paper is white. That seems obvious. So we want to say A. The whiteness is a feature of the paper. Yet he also wants to say that whiteness is in our mind, a feature of our perception of the paper. So the whiteness is in our mind. He then concludes that the paper is also just a feature in our minds, what he calls an idea. As I discussed in the last post, you might think of this more as an image (though he thinks of all the five senses as leading to ideas in our minds).

There are two possible criticisms of the argument (two ways of diagnosing where it might go wrong):

1. When we discover whiteness to be a property of mental images, that means whiteness isn't really in the paper. It's a property of our ideas, not of the paper. The paper has structural molecular properties that cause us to see whiteness, but whiteness isn't in the paper.

2. Whiteness is in the paper, but it's not the same whiteness as mental perception. The whiteness of the paper is a structural feature of the paper, and the whiteness of the image is a visual representation of that structure. It's a feature of our experience, not of the paper. Both views both agree that the argument makes a mistake, but they differ on what they think the specific problem is. The difference is really just whether you want to continue to use the word 'whiteness' to refer to the structural properties of the paper.

So that argument clearly has a response, though it's not obvious which one is right. They can't both be right, but the existence of two possible responses makes it a fairly unconvincing argument if there are two easy ways to avoid the conclusion.

Berkeley's other argument isn't so easily defeated. He relies on a principle known as Ockham's Razor (alternatively spelled Occam's Razor by Latin purists, but William of Ockham was English):

If you have two theories that both equally explain the evidence, and one of them has a lot of excess stuff built in, then you should believe the simpler theory.

Ockham never, to my knowledge, stated such a principle (and neither did Berkeley, as far as I'm aware), but its place in the history of philosophy derives from some of Ockham's arguments even if he didn't state it as a principle, and Berkeley clearly had the same sort of thing in mind, even if he was using it for a very different issue. The name comes from the process of simplifying a theory. It's as if you shave off all the excess baggage that the theory doesn't need, since it explains the evidence without all that.

Berkeley compares the two theories, with something like this principle in mind. He believes in minds that perceive ideas. There are just those two kinds of things. Someone believing in an external world, however, believes in those things plus the existence of all these external objects. Both theories explain perception and how we can interact with other minds, and each theory explains the evidence perfectly well. So we might as well believe Berkeley's idealist theory, since it doesn't require all that extra stuff. Idealism accepts the minds and ideas that everyone else already believes in, but it cuts out what's not needed to explain the evidence. If you can explain all the evidence based on a theory that basically treats our experience as if we're in the Matrix but without the computers, then why believe in the external stuff? Berkeley's theory is much simpler, and simpler theories tend to be more likely to be true, largely because they don't add in unnecessary features that aren't needed to explain what we're sure of (our experience).

People who believe in the external world that the ideas are supposed to be ideas of will criticize Berkeley's argument for ignoring the fact that his theory has God organizing all our ideas, kaking sure they conform to the laws of nature and allowing for genuine interaction with other people. Berkeley is aware of this fact, but he just says that God is one more mind, of the same kind of thing as all the other minds we all believe in. He's more powerful, but he's a mind, and minds and ideas are all there are. The external world is a whole bunch of things beyond that, and they’re of a completely different kind of thing. So Berkeley still has fewer kinds of thing. That's not enough for someone like van Inwagen, though, since he says Berkeley builds too much work for God into his theory. It's not that he has extra kinds of things, but he's got all this extra work for one infinite mind to be doing. Philosophers disagree on how to resolve this dispute. Each side seems to be relying on a different kind of simplicity, and both kinds seem relevant to Ockham's Razor.

The arguments for and against idealism thus don't seem very conclusive. If Berkeley is right, we do have something to say to the skeptic, and it seems as if the strongest argument against idealism (turning Ockham's Razor back on it) isn't any stronger than the arguments for idealism. Still, it would be hard to convince the skeptic that idealism is right, and thus it's going to be hard to say what Berkeley wanted to say, that the skeptic has been refuted.

Up Next: Sidebar on Theories of Perception


Thanks for these posts on Berkeley. I have been fascinated with this theory of perception, and his response to skepticism for quite some time. I also like the fact that his philosophy pretty much does away with all of the problems in the philosophy of mind, like the interaction problem. Wasn't Johnathan Edwards something of an "ideaist also?

Blake Reas

Edwards had one substance -- God -- and one cause -- also God. Every other substance and cause are only pseudo-substances and pseudo-causes. Since they derive all their causal power from God, only God is a genuine cause. He applies similar reasoning to the existence of reality that's dependent on God -- its reality depends on God, and thus it isn't real in itself. He thinks what makes me-now and me-in-ten-minutes the same person is that God decrees it so.

I'm not sure this really amounts to idealism, although you can probably frame it that way. I think it's more that he held a divine command theory about which things are real, which combinations of things are substances, and which occurrences cause which others. It's a way to have a stronger sense of divine sovereignty, not a way to diminish the reality of the physical world.

Jeremy, Is the first argument really fatal to Berekeley? It doesn't seem to matter whether or not the idea is "external" to us, because aren't they kept in existence, and get their nature from God? So why would it matter if the idea of white, or paper is in our mind, or "external"to our minds, since they have their "absolute" being in God's mind. Our thoughts are derivative so to speak. We don't create these ideas after all. Have I misunderstood?


Strategy 1 isn't an argument against Berkeley's view. It's not, in that sense, fatal to Berkeley's view itself. It's a criticism of Berkeley's argument. Berkeley's argument has two premises, and one of them is false if strategy 1 is correct. So it's a way to resist his argument and retain belief in the external world. It's not an attempt to show that his view itself is wrong. You'd have to say more in support of belief in the external world to do that. But it does show that this argument need not be convincing to those who do believe in an external world.

The simpler assumption, in my opinion, is that the existence of an external, physical world is what causes our sensory perception of it. How did the mind produce the 'idea' of a fundamentally different kind of reality (spatial)than itself? Our existence is so tied up with the physical world, it would be so drastically different if we didn't have the 'illusion' of having a body and being able to move through space and interact with our environment (it would be hell, we would be paralyzed with no sensory perception). Why would the mind create this other reality that it's so dependent on? Even if sensory perception is mental, the objects of our sensory perception are not.

Yes, that's basically Thomas Reid's response to Berkeley.

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