Philonous: To put it past all doubt, consider the following. If colours were real properties or qualities inhering in external bodies, they couldn't be altered except by some alteration in the very bodies themselves: but isn't it evident that the colours of an object can be changed or made to disappear entirely through the use of a microscope, or some change in the fluids in the eye, or a change in the viewing distance, without any sort of real alteration in the thing itself? Indeed, even when all the other factors remain unaltered some objects present different colours to the eye depending on the angle from which they are looked at. The same thing happens when we view an object in different brightnesses of light. And everyone knows that the same bodies appear differently coloured by candle-light from what they do in daylight… Now tell me whether you still think that each body has its true, real colour inhering in it. [From Three Dialogues between Hylas and Philonous in opposition to Sceptics and Atheists]

I'm just slamming that hapless materialist, Hylas, here. Or, to be more accurate, I should say that the character "Philonous" is slamming Hylas (I know as the author I'm not supposed to overly identify with any of the people in the dialogue, but it's kind of hard to remain aloof in this case. Take that, Roland Barthes.)

So, in this section, Hylas is doing his best to argue that the world consists of mind-independent material objects that we learn about through our senses. In particular, he claims that qualities like colors are objectively inherent in the objects themselves. Can you believe the airhead-ocity?

Wait—you're on team Hylas? What? Well, look, if colors were objective aspects of objects, then they wouldn't appear different to different observers under different conditions, would they? Things would look the same regardless of the light, or the angle from which you viewed them. They'd look the same if you were a fly or a dog or a fish. It shouldn't matter, either, what state your eyes are in—whether you have cataracts, or floaters, or what have you.

But even those unfortunate members of team Hylas know things aren't like that. Which means… which means… it's okay, I'll wait… that's right: it means that colors—and, by extension, other qualities like sounds and smells—don't inhere in objects. They are sensible qualities, which is to say, qualities that depend entirely on the observing mind for their existence.

Score another one for Berkeley... I mean Philonous.

Hylas: But when on the other hand I look in a different way at sensible things, considering them as so many properties and qualities, I find that I have to suppose a material substratum, without which they can't be conceived to exist.

Philonous: Material substratum you call it? Tell me, please, which of your senses acquainted you with it?

Hylas: It is not itself sensible; only its properties and qualities are perceived by the senses.

Philonous: I presume, then, that you obtained the idea of it through reflection and reason…

Hylas: I don't claim to have any proper positive idea of it. But I conclude that it exists, because qualities can't be conceived to exist without a support… Isn't [its relation to those qualities] sufficiently expressed in the term 'substratum' or 'substance'?

Philonous: If so, the word 'substratum' should mean that it is spread under the sensible qualities… And consequently spread under extendedness…Tell me, Hylas, can a thing be spread without being extended? Isn't the idea of extendedness necessarily included in that of spreading?... Consequently every bodily substance, being the substratum of extendedness, must have in itself another extendedness which qualifies it to be a substratum, and that extendedness must also have something spread under it, a sub-substratum, so to speak and so on to infinity. Isn't this absurd in itself, as well as conflicting with what you have just said? [From Three Dialogues between Hylas and Philonous in opposition to Sceptics and Atheists]

I love this part. Philonous has got Hylas on the run, but Mr. Matter-man isn't quite ready to admit defeat. It's so wonderful to watch his last flailing efforts at defending his materialist position, before he is finally and utterly vanquished. Not that I, a man of the cloth, could ever take pleasure in the sufferings of another, of course.

So Hylas has previously been forced to concede that matter cannot be identified with any sensible qualities. After all, anything sensible is immediately perceived; anything immediately perceived is an idea; and ideas only exist in minds. But, stubborn man that he is, Hylas still wants to find some meaning for the term "matter," and so he suggests that it must be the "substratum" which supports all those qualities we observe.

Matter is thus now held to be some kind of unobservable, unknowable floor spread under the world's perceivable qualities. Materialists can be very imaginative in coming up with new ways to hold on to their pet notions; I'll give them that much.

But Philonous is relentless, as genuine seekers after truth must be. What does it mean, he wonders, to say that this material substratum is "spread under" observable qualities? Sure, we can make sense of this—if we think of something like a floor lying underneath a rug or something, the rug being everything in the world we can actually observe.

But if that's the kind of thing Hylas is thinking of, well, then it shows that this supposedly unobservable "substratum" is (secretly) conceived of as having extension, meaning that it's something that takes up position in space. But "extension" is just another feature of physical objects; it's one of those qualities that Philonous has already shown to be immediately perceivable, and therefore it is something that exists only in a mind.

That would mean that Hylas would have to assume another substratum spread under this extended substratum, as a mind-independent, material "support" for this quality. But then, since this new substratum would also be extended, there would have to be yet another substratum under it, and so on and so forth. In a word: it makes no sense.

Okay, that's four words, so how about just this one: fail.

It is but looking into your own thoughts, and so trying whether you can conceive it possible for a sound, or figure, or motion, or colour to exist without the mind or unperceived. This easy trial may perhaps make you see that what you contend for is a downright contradiction. Insomuch that I am content to put the whole upon this issue: If you can but conceive it possible for one extended movable substance, or, in general, for any one idea, or anything like an idea, to exist otherwise than in a mind perceiving it, I shall readily give up the cause. And, as for all that compages of external bodies you contend for, I shall grant you its existence, though you cannot either give me any reason why you believe it exists, or assign any use to it when it is supposed to exist. [From A Treatise Concerning the Principles of Human Knowledge]

This is what people often refer to as my "Master Argument." It's the key moment where I definitively show that "to be is to be perceived."

The argument is very simple—that's the beauty of it. Give me an example of a material object (or quality, or anything at all) that can exist without being perceived. Got one yet? Well, whatever you come up with is something that you are thinking.

Clearly, then, it follows that to exist is always to exist as an object for some mind or other; it is to be perceived. An entity that is incapable of being perceived, by contrast, is no entity at all.

There's simply no way around it, which is why they call this the Master Argument.

Hylas: Real things, obviously, have a fixed and real nature which remains the same through any changes in our senses or in how our bodies are placed or how they move. Such changes may indeed affect the ideas in our minds, but it would be absurd to think they had the same effect on things existing outside the mind.

Philonous: How, then, can things that are perpetually fleeting and variable as our ideas are be copies or likenesses of any thing that is fixed and constant? Since all sensible qualities—size, shape, colour, etc.—that is, our ideas, are continually changing with every alteration in the distance, medium, or instruments of sensation, how can any fixed material object be properly represented or depicted by several distinct things or ideas, each of which is so unlike the others?… There is more. Are material objects in themselves perceptible or imperceptible?

Hylas: Properly and immediately nothing can be perceived but ideas. All material things, therefore, are in themselves insensible, and can be perceived only through ideas of them.

Philonous: Ideas are sensible, then, and their originals—the things they are copies of—are insensible?... But how can something that is sensible be like something that is insensible? Can a real thing, in itself invisible, be like a colour? Can a real thing that isn't audible be like a sound? In a word, can anything be like a sensation or idea but another sensation or idea? [From Three Dialogues between Hylas and Philonous in opposition to Sceptics and Atheists]

Okay, I think this bit may sound a tad more complicated than it actually is. I'm sure it's hard to give up on the view that the ideas in our heads are copies of something else outside of them in an unthinking, independent material world. But basically, all I'm showing here—through my loyal spokesman Philonous, natch—is that this notion makes no sense, however attached to it we may be.

Think about it. Our ideas change more quickly than Rihanna's hair. But materialists like Hylas claim that so-called physical objects are stable and unchanging. So how could our changing ideas be a copies of unchanging physical objects?If our kaleidoscopic ideas were actually imitating something else, it sure couldn't be a realm of fixed, permanent phenomena.

And it's even worse than that. Hylas has been forced to acknowledge that whatever is immediately sensible is an idea. His beloved matter, therefore, has to be something insensible, something not available to the senses.

Fine, we'll give him that. But this only shows that our ideas and material things have absolutely nothing in common. The point, again, is simple. If our sensible ideas don't have the faintest resemblance to material objects, we can't meaningfully talk about our ideas as copies of material objects.

For those of you keeping score, I believe that now makes it Immaterialists 97, Materialists 0.

Philonous: When I say that sensible things can't exist out of the mind, I don't mean my mind in particular, but all minds. Now, they clearly have an existence exterior to my mind, since I find by experience that they are independent of it. There is therefore some other mind in which they exist during the intervals between the times when I perceive them; as likewise they did before my birth, and would do after my supposed annihilation. And as the same is true with regard to all other finite created minds, it necessarily follows that there is an omnipresent, eternal Mind which knows and comprehends all things, and lets us experience them in a certain manner according to rules that he himself has ordained and that we call the "laws of nature." [From Three Dialogues between Hylas and Philonous in opposition to Sceptics and Atheists]

This "to be is to be perceived" business bothers a lot of people. Suppose I get hit on the head and knocked unconscious. Does this mean the world just disappears? That would be simply ludicrous.

Well, here's my answer to all you doubters out there, and it's an answer that totally reveals my inner bishop-ness. No, I say, the world does not disappear if I die or become unconscious. And, no, that does not mean that external objects have a mind-independent existence, either. Instead, everything continues to exist just as before—in another mind.

But whose mind would that be? Reality cannot depend only on the minds of other people, since they too could go out of existence. Nope—what is required is an infinite mind. Yes, that's right: it's the mind of God that continually perceives all ideas and ensures their ongoing existence.

Thus, we have a very simple and direct proof of God's existence. A supreme intelligence must be assumed in order to make certain that the world is not always popping in and out of existence. And all those ideas of yours that you think refer to an external, physical universe. Those are simply ideas in the mind of God.