h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

One difference between rainbows and ordinary objects is that viewing of ordinary objects results in the perception of actual properties(i.e. when we view a table we percieve it's actual physical structure -- its flat surface, four legs, etc.) whereas viewing a rainbow results in the perception of false properties(the colorful circle we percieve has no actual referent). Our brains are being fooled. This is true of any optical illusion. In such cases, the "object" percieved is supervenient and the physical properties of its referent must be inferred.

Sorry for my delay in replying. Your assertion fascinates me.

What is illusory about the sun? That is the thing seen. The circle we see is the shape of a collection of mirrors: those droplets which are placed so as to reflect the sun to us. Nothing false there either.

Is it a false property of this selection of droplets that it is circular?

No worries.


Actually, the droplets act as prisms, not mirrors. If they acted as mirrors rainbows would look like the sun. The light from the sun is altered by the droplets causing us to percieve something that resembles neither of the things responsible for the rainbow. As a result, we have three distinct "objects" to deal with here. 1) the sun, 2) the cloud of droplets, and 3) the rainbow. In reality there are only two actual objects -- the sun and the cloud of droplets. The third(the rainbow) is illusory. It has no actual referent. Neither the cloud of droplets or the sun are rings of multi-colored concentric circles. Therefore, neither the sun or the cloud of droplets is the actual referent of the rainbow. It has no actual referent.

Worries.

So . . . let's see, you're saying: if I look at something through the medium of a prism, I don't see it, I see something else that can't be it because it doesn't look like it?

Well...what does it mean to "look at something"? Does it mean "to have the photons emanating from something hit us in the eyes"? By this definition, we only ever see the sun(or lightbublbs) since the sun is where the photons originate. Conventional usage, however, entails that seeing something means interpreting the light that reflects from the surface of an object.

If a prism has the properties: composed of crystal, 6 cubic centimeters, translucent, colorless

...then to see this prism means seeing these properties. If we attempt to look at this prism but instead see a 12 foot tall pink elephant, then we are not seeing the prism -- we are seeing the properties of some other object that doesn't resemble the prism in any way. This can be due to either an illusion(an external fooling of the senses) or a hallucination(an internal fooling of the senses). In either case, the object percieved does not exist.

In the case of rainbows, we are not perceiving the properties of any known *actual* object. The tree outside my window is an *actual* object. The properties I percieve from this tree are identical to the actual properties of the tree. Just as important is that when I close my eyes the tree is known not to cease to exist. A rainbow is not an *actual* object. The properties percieved are illusory; and when I close my eyes, it is know to cease to exist. It is an optical illusion created by the refraction and dispersal of light.

Good . . . but not good enough

You seem to be saying that there is no circular striped object out there that has any existence beyond being perceived. I on the other hand seem to be arguing that its perception is sufficient to guarantee its objectivity. This is the standpoint of Berkeley, with whom I do agree: A3472986

However, let's continue without taking Berkeley into account. Your last claim is extremely dodgy, that a rainbow is known to cease to exist when viewers close their eyes. This is not my experience. The rainbow is as reliably there as any other feature of the landscape. Several people can view and discuss (sensibly) a rainbow together. Do the thought experiment.

A subjective idealist! I thought you had all died out...

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Recumbentman said:

"The rainbow is as reliably there as any other feature of the landscape."
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I disagree. By looking at a tree, I can make accurate predictions about its causal effects based on its percieved properties. For instance, I can predict that if a bird attempts to land on one of its branches, the bird will have something on which to land. The same cannot be said of the rainbow. While the percieved properties of the rainbow are indicative of a physical substantial object, it is only through inference that we determine its non-substantial nature. Our perception of the rainbow taken at face value would require us to predict that if a bird attempted to land on it, it would have something on which to land!

Supervenience is an essential property of illusions; actual objects are necessarily non-supervenient; therefore, the essential properties of illusions and actual objects are not the same(ergo, rainbows are not actual objects).

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Recumbentman said:

"Several people can view and discuss (sensibly) a rainbow together."
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True. However, just because several people become subject to the same illusion it doesn't somehow make that illusion real. The illusion may objectively exist(to the extent that multiple people are subject to it), but it remains a illusion. An entire audience may be witness to a magic show yet the magician still does not cut the pretty girl in two...

Subjective idealist my foot. Empiricist.

>Our perception of the rainbow taken at face value would require us to predict that if a bird attempted to land on it, it would have something on which to land!

The same could be said of clouds. But of course, they are just illusions too, would you say?

>An entire audience may be witness to a magic show yet the magician still does not cut the pretty girl in two...

But all I'm saying is, they have really seen something. Descartes threw out the baby with the bath water when he said our senses are not to be trusted at all, because they are capable of being deceived.

Recumbentman said:

"The same could be said of clouds. But of course, they are just illusions too, would you say?"

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Clouds seem pretty gaseous to me. I don't think there's anything in the percieved properties of a cloud that belies its gaseous state.

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Recumbentman said:

"But all I'm saying is, they have really seen something. Descartes threw out the baby with the bath water when he said our senses are not to be trusted at all, because they are capable of being deceived."

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I basically agree. But we must be careful not to commit the fallacy:

"Our perceptions *can* have actual referents, therefore *all* our perceptions have actual referents."

Some form of empiricism is necessary for predicting observations(i.e. science), but to go from this pragmatic position to a metaphysical one of hard realism is unwarranted, IMO.

>I don't think there's anything in the percieved properties of a cloud that belies its gaseous state.

And rainbows? Do they belie their state? They're not seen in dry weather, so they obviously have something to do with the wet. And I seem to remember you hinting that *some people*. not you of course, might take them to be as solid as trees, and expect birds to be able to land on them . . .

I'm putting words in your mouth, OK. But you are putting words in my mouth. Reality comes in all degrees, and "actual" is in the end a fuzzy concept, not a hard one. It's not much help saying "actual things are like trees and tables -- things you can see and touch and predict their other properties". Not all actual things are of such manageable size, or have such simple contours.

Is economics an actual thing? If not, is the study of economics an actual thing? If not, is a course in economics an actual thing? If not, are people deceived when they pay for one?

Recumbentman said:

"And rainbows? Do they belie their state? They're not seen in dry weather, so they obviously have something to do with the wet."

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This is an inference. We cannot obtain this knowledge(that 'they obviously have something to do with the wet') simply from the sensory data of rainbows. We must place our perceptions in the context in which rainbows appear and then use *reason* to infer that rainbows involve water droplets. Do you see the important distinction, here?

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Recumbentman said:

"And I seem to remember you hinting that *some people*. not you of course, might take them to be as solid as trees, and expect birds to be able to land on them . . ."

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This is a strawman. My claim was that *if we only rely on our sensory data of rainbows*, THEN we would be *required* to predict that they have the same properties as any solid object(more or less). Matter only has three states on earth. Solid, liquid and gas. If rainbows looked like gas they would simply blow away(just like clouds). If rainbows looked like liquid they would splash down to earth. Because they hold their shape -- in midair no less -- they appear to be solid. Because they *appear* to be solid, if we only rely on *appearances* we must think them solid. Obviously, anyone with experience seeing rainbows and a modicum of *reason*(not sensory data) would not think them solid objects; but this conclusion is reached through reason -- not perception.

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Recumbentman said:

"Reality comes in all degrees, and "actual" is in the end a fuzzy concept, not a hard one. It's not much help saying "actual things are like trees and tables -- things you can see and touch and predict their other properties". Not all actual things are of such manageable size, or have such simple contours."

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In the context of this discussion(ontology) the term "actual" refers to hard physical existence. In other words, an object that subsists in external reality independently of humanity. If all life capable of perception was wiped out, an *actual* object would continue to exist(I don't want to get into the realism/idealism debate, here. It won't shed any light on this discussion. If we assume realism, then actual objects exist. If we assume idealism, then this conversation about external reality is meaningless).

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Recumbentman said:

"Is economics an actual thing? If not, is the study of economics an actual thing? If not, is a course in economics an actual thing?

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None of these are actual. They are social constructs that describe the relationships between actual things(and other social constructs -- like money -- which, in turn, describe the relationships between other actual things). There are no substantial physical objects that any of these terms refer to.


I think the problem here is that you are confusing "actuality" with "existence". Toss the term "being" in the mix and add a dash of Heidegger and we'll really be screwed up!

Anything can be said to exist so long as there are properties attributable to it(this is very conventional -- there are positions that don't take this as true). In this sense, rainbows can be said to exist. However, this is not the same as saying they are actual. In order for rainbows to be actual, they would have to subsist in external reality independantly of perception.

OK, you exclude social constructs from actuality. Is sunshine actual?

Recumbentman said:

"OK, you exclude social constructs from actuality."

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Yep; as does standard philosophy. Actuality is not the same as objective existence. Social constructs objectively exist but they only exist as interactions between people. Remove the people(or the interactions) and the social construct ceases to exist. Clearly, there is no actual object subsisting externally that a given social construct refers to.

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Recumbentman said:

"Is sunshine actual?"

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If by "sunshine" you mean "photons"(or EM radiation), then yes, photons are actual. Of course, the closer we move to QM the less philosophy has to say, ontologically speaking.

Are there photons in rainbows?

Recumbentman said:

"Are there photons in rainbows?"

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No. Photons "carry" sensory data about objects that is taken in by the eyes and processed into visual qualia by the brain. This is perception. When a perception has an actual referent, that referent can be said to exist in actuality. When a perception does not have an actual referent, that referent cannot be said to exist in actuality as there IS no actual referent. How can something that isn't there be said to exist in actuality? In the case of rainbows(or any illusion), the perception has no referent in actuality. Close your eyes and the rainbow you are seeing no longer exists.

Lets assume for the moment that rainbows are physical objects. If something has no causative effects it cannot be said to exist physically. So what can rainbows, as physical objects, be said to have causative effects on? Well, perception...and nothing else. They don't cause gravitational effects, they don't give off particle emissions, they don't increase the entropy of a system in any way. Because the only causative effects rainbows could be said to have are through perception, then when you close your eyes(no longer perceiving the rainbow) it has absolutely no causative effects. If this is true, then you must commit to the position that rainbows stop physically existing when you close your eyes. You must claim that physical objects can pop into and out of existence literally at the blink of an eye. This in no way corresponds to our basic understanding of the nature of empirical reality -- physical objects are simply there whether we perceive them or not.

I think this is where this conversation stops; photons are an essential element of my rainbows, but not, apparently, of yours.

And yet we could stand side by side and discuss a rainbow we both saw. We could, if you felt like it, close our eyes one at a time and say, "Still there?" -- "Yep! What did you expect?"

And would we be deceived in thinking that we were seeing the same thing? You say yes, I say no.

It seems to me that you beg the question by asking "How can something that isn't there be said to exist in actuality?"

It is there. Reread the Entry.

Recumbentman said:

"I think this is where this conversation stops"

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If you wish.

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Recumbentman said:

"photons are an essential element of my rainbows, but not, apparently, of yours."

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How can photons be an element of anything other than light? The notion doesn't even make sense. There are no photons in trees or dogs or planets. Photons are radiation that bounces around the universe and occasionally hits us in the eyes. They aren't parts of other things. Please explain this.

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Recumbentman said:

"And yet we could stand side by side and discuss a rainbow we both saw. We could, if you felt like it, close our eyes one at a time and say, "Still there?" -- "Yep! What did you expect?"

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This is objective existence. We both agree that the experience "rainbows" has objective existence. For some reason, you refuse to even acknowledge the difference between objective and actual existence. They are not the same.

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Recumbentman said:

"And would we be deceived in thinking that we were seeing the same thing? You say yes, I say no."

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We would be having roughly the same experience. However, your assertion that we would be seeing the same rainbow is quite easy to refute. Here's how:

If we are both seeing a rainbow that looks exactly the same but your rainbow is in London and my rainbow is in Tibet, then we are not seeing the same rainbow(obviously).

If we are both seeing a rainbow that looks exactly the same but your rainbow is in London and my rainbow is in London but 2 miles down the road from yours, then we are not seeing the same rainbow.

If we are both seeing a rainbow that looks exactly the same but your rainbow is in London and my rainbow is in London but 2 inches down the road from yours, then we are not seeing the same rainbow.

Now, I am sure you've noticed that if you are moving while viewing a rainbow, the rainbow seems to move along with you. This means that the location in space that the rainbown has is dependent on the location of the viewer. Because of this, when we stand next to each other your rainbow is not in the same location as my rainbow. If we compared measurements from our respective locations, we would find that the location of our rainbows would differ. If it's a large rainbow, probably by several feet or more. This clearly shows that because each of our rainbows is in a different location, they cannot be the same rainbow. It doesn't matter whether they're thousands of miles apart or only a few inches apart.

BTW...I didn't just come up with this argument. It called Leibniz's Law.

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Recumbentman said:

"It seems to me that you beg the question by asking "How can something that isn't there be said to exist in actuality?"

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If my argument were: "Rainbows aren't there, therefore rainbows aren't there" that would be begging the question.

Fortunately, that isn't my argument. The *conclusion* of my argument was "rainbows aren't there". The statement you chose to highlight was simply me pointing out that my conclusion conradicted yours.

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Recumbentman said:

"It is there. Reread the Entry."

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Which entry should I reread. I don't recall seeing you make a valid argument. Perhaps you should state your argument clearly so that I may see where I am mistaken.

One of my favorite things in life is having a position I hold as true be shown to be mistaken. It is in these times that I learn the most and learning is why I do philosophy. It is a shame that not everyone that does philosophy(even if they only dabble) feels the same...

Is it to wind me up you ask "which entry"? Clicking the blue letters at the top of the page bring you to the entry for which this thread is a discussion forum.

In that entry you would see that I claim "it is not enough of an explanation to say that a rainbow is merely the effect of sunlight on water vapour; the same can be said of how we are able to see clouds, but no-one calls clouds illusory. (Cloud illusions may indeed be more memorable than the real things: still, there is a real cloud, and there is equally real stuff out there wherever a rainbow is seen.)"

This is what I took you to be disputing. Neither of us appears to be convinced by the other's words, to our mutual amazement.

One of your distinctions that amazes me is "For some reason, you refuse to even acknowledge the difference between objective and actual existence. They are not the same." To me they are. Objective, actual: that is to say not imaginary, not subjective. I try to follow Wittgenstein A1024156 in this distinction, but I do not at the moment manage to follow you.

Another amazement to me is your paragraph beginning "How can photons be an element of anything other than light?" Rainbows are indeed made of light. What am I missing here?

Finally (for now, if you want to go on, and I must say I haven't had a good natter like this for a long while) the question of seeing a different rainbow or the same rainbow a thousand miles, two miles, or two inches apart is one of the wonderful surprises that can be extracted by thinking hard about the rainbow. As I said on another thread, in one sense it is always the same rainbow we see; there is only one.