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Starlight - Messages from the Past?

What is light? Physics and M. O'C. Drury's criticism of the notion that light is a thing. The grammar of the word 'light' is not name-of-object.

Outline of this page ...


Introduction: Drury and "the danger of words"

The original sin in philosophy, according to Wittgenstein, is treating all words as if they were the names of things (as in "person, place or thing" (nominalism (PI § 383)), although the uses of nouns are most varied. When even "abstractions" are assumed to be names, they seem to give us some thing to hold onto, even if there is nothing there. For example, "What is a concept really?"

Popular books on astronomy tell me that when I look at the great nebula in Andromeda I am really seeing something that was contemporary with millions of years ago ....

Here again the word 'velocity' has led us astray. We imagine some thing that, leaving the nebula, travels through the immensity of space .... surely there must be something that moves. A stream of photons? A wave motion in an unknown medium?

Yet the experiments [from which were derived the velocity of light] reveal no such entities. (M. O'C. Drury, "Fact and Hypothesis", in the journal The Human World, Volumes 15-16 (1974), p. 137)

What is Drury's argument here? Is it only that in science: If you do not know how the results were derived, then you do not understand the conclusion -- i.e. theory -- based on those results? No, it is also that light is light, and not some other thing.

At school we are required to understand -- or to pretend we understand -- in order to pass exams -- the meaning of such "signs" (i.e. ink marks on paper, spoken words) as 'speed of light', 'photon', 'light wave'. Doing well on the exam -- that is the criterion for saying that someone 'understands' or 'does not understand' (Understanding is a public event). We learn to play a game (as in "language-game"). -- And do not say that a move in a game cannot be nonsense, because nonsense is exactly what has been taught about the "grammar" of the word 'point' in geometry for thousands of years.

The word 'light' as the name of some thing. What that suggests to us is a picture: that light leaves its source [the light bulb], bounces off the clock hanging on the far wall -- and that this reflected light carries an image of the clock to our eyes. The expression 'the speed of light' would then mean how fast the thing called 'light' takes to make this image-carrying journey. That is the picture, but is it a picture to which there corresponds a reality? If we do not know how to verify or falsify a picture, then it is pure metaphysics (imagination).

"The speed of the image-carrying light." We might picture the Australian colonists waiting for the newspapers to arrive by ship from England. These voyages take weeks, months. And so even though the papers say "TODAY'S NEWS", what is printed in them is not what happened in London yesterday, but what happened there weeks ago. If the paper says "Hanging tomorrow", that does not mean that if the colonists were magically transported to London they could attend the hanging; no, the hanging and cremation already happened, weeks, months, ago.

And so we think: light from the stars: it works the same way: the thing named 'light' carries information to our eyes [as it were a newspaper photograph] about of what happened millions of years ago. But in what sense can 'light carry' anything? Do we know what that expression might mean? Would it be as if a god would see a cartoon being projected though the air to our eyes frame by frame by frame, each frame being carried by a fragment of light; or would the god see an undulating wave, each undulation carrying a frame of the picture?

Einstein said that he imagined himself traveling on "a beam of light", as if light were something he could sit on like a trolley car. And we can also picture light as a series of photons or as a continuous wave. But such pictures are pure theory: photons and waves are theoretical constructs, consistent with the facts, but not facts themselves. They have never been seen.

"An image projected though the air to our eyes frame by frame by frame." -- But that picture is consistent with any and all facts; unlike the best of scientific theories it cannot be falsified by anomalies. ("The limit of science is -- concept-formation" What does it mean? Conceiving a problem in such a way that it can be solved is the difference between imagination in science and mere fantasy.)

Andromeda millions of years ago ("the velocity of light")

If a theory is divorced from the evidence it summarizes, is it divorced from its meaning?

The word 'force' is without force, i.e. without meaning, if the method by which force is to be measured is not specified. Likewise the expression 'the speed of light' is without meaning unless how the speed of light to be measured is specified. 186,000 miles/second is a measurement of speed -- but it does not in itself say what that speed's relationship is to light: the word 'light' is not the name of an object; and as a phenomenon light is nebulous.

With respect to "the velocity of light". First there was an observation. Then an hypothesis was formed about the observation. Then an experiment was set up [devised, invented] to confirm [test] the hypothesis -- i.e. to see whether the hypothesis was consistent with the observation.

M. O'C. Drury wrote (in "Fact and Hypothesis", p. 137) that a very high degree of skill and instrumentation was necessary to do these things. But that if this background is not mentioned, and we hear the phrase 'the velocity of light', then "imagination comes into play". And we imagine that if there is velocity "then there must be something that moves". And various things are suggested, e.g. photons, waves. But "the experiments reveal no such entities".

And in this way Drury says that "Light is light, neither particle nor wave", that photons and waves are creations of the imagination. As the motto Everything is what it is, and not another thing -- i.e. not "really" something else instead -- implies: Light is not really something else, something supra-sensory.

Reality which lies before us at every moment is replaced by the abstract picture we have ourselves created. (Drury, The Danger of Words (1973), p. 100)

As in the case of atoms in space -- "We are so used to this picture that it's as though we had all seen atoms" (LC p. 17) -- imagination allows a theoretical construct (which is in this instance a bit of ancient Greek metaphysics) to replace the solid table which stands in front of us.

Is there a word more dangerous to the understanding in philosophy than 'really'? (Well, 'meaning', 'abstract object', 'the same', for example.) "What is light -- really?" As if the question for philosophy were Platonic: What is the essence of light? rather than logical: How do we use the word 'light'?

"The Stars in the Night Sky are not Real"

"The stars we see in the night sky do not belong to the present; their reality is in the past. Many are the light from lamps long ago extinguished." In other words, what we see is not really (what is) there. Question: Are the pictures this language suggests to us the meaning of the hypothesis? Or are these pictures idle -- like the pictures suggested to Augustine by the question "What is time?" (PI § 89)

And why should such a picture be only an imperfect rendering of the spoken doctrine? Why should it not do the same service as the words? And it is the service which is the point. (ibid. II, iv, p. 178g)

Andromeda snaps: "... in Andromeda I am really seeing something that was contemporary with millions of years ago." The difficulty is not in inventing pictures to give a sense to those words. The difficulty is saying what relation, if any, those pictures have to reality; -- i.e. is what the picture we invent says the same as what the theory says?

We are all familiar with a beam of light. What do we mean? -- We switch on a flashlight [torch] in a dark room and immediately we see a path of light, light confined to a particular space, contained in a envelope, (Here a sketch or a photograph would explain the meaning of 'beam of light' better than words, if, that is, we were not already well-acquainted with this phenomenon).... But is the word 'light' the name of some thing?

Is 'beam of light', then, not the name of anything? No more than 'space' is the name of anything when we say e.g. 'There is a space on the shelves over there where the books will fit' or 'Here, you must push the square pegs through the square holes (spaces). [Is the word 'hole' a name? is that its use in the language toolbox?]

Very well, pushing such difficulties aside [-- because they expose the nonsense hidden in the question --], we are told that light travels at a certain speed, -- which means? That our beam of light does not reach the other end of the universe immediately we turn on the flashlight: it takes time to get there. How do we know that -- i.e. how might we measure this?

If the universe is round, like the soap bubble picture (Einstein: The universe is finite but unbounded), then we can make the observation ourselves: we position e.g. an oil-painting behind the flashlight and facing in the opposite direction from the flashlight, then we turn on the flashlight and measure the time that passes before the painting is illuminated. If the universe is very big, this could take quite a bit of time, if the speed stated in the theory is correct.

As was said, inventing such a picture is not the difficulty. But does such a picture do the same service (PI II, iv, p. 178g) as 'the theory of the velocity of light' does? Is it consistent with the evidence -- and does it summarize the actual evidence in a satisfying way -- or is there too much fancy in our picture, even though it is consistent with the evidence? (Is our picture consistent with the evidence? Certainly not with the evidence provided by our everyday experience. But perhaps by that same type of evidence the earth is flat.)

Now, imagine that we set up two motion-picture screens, one in front of the beam-of-light-source [e.g. a motion-picture projector], the other behind it; the screen behind the source is the opaque type we are familiar with [from the movie theater]; but the screen in front of the source, although the beam illuminates it, does not diminish or alter the beam of light in any way. Now, if we run a film in front of the beam-of-light-source -- e.g. the bulb of a motion-picture projector --, then we can say that an audience looking at the first screen will see the images before an audience looking at the second screen (i.e. the opaque one behind the light-beam-source) will.

"What is Light?"

Aside. White is not the only color of light. Indeed, white is not the color of any light. Further, indeed, light is not any color at all. Light is without color -- "clear as glass" as it were; were it opaque it would not allow us to see anything but itself; as Wittgenstein noted, there is nothing we call 'transparent white' [Note]. It is true that we can pass the light from a source through colored glass or through a prism and see what we call "colored light". However, if we remove the glass, if we remove the prism, then we do not see "colored light". Light is without color. What might be said is that when we shine a light source on colored glass or on a prism, what we see is colored air. If there were no air -- particles of dust, that is -- then we would not see "colored light" [or any indication of light whatever; indeed, light would be absent]. Indeed, if the universe were devoid of objects, then, although a billion light bulbs were shone on it, it would remain in darkness [black]. Where there is nothing to illuminate, there is no light.

When we say that a prism "divides white light into its component parts", are we suggesting anything more than a picture of events (It is surely not an hypothesis)? What is unverifiable -- because it is nonsense -- is that "white light" can be "divided into component colors". Light is not any color. The word 'light' is not a name; it is not defined ostensively. It is not the name of some thing; it is not the name of anything. There are indeed light sources that we can point to, candles, the sun, stars, light bulbs -- however, these themselves are not light; they are sources of light, but they are not light. There is no place to look to find light. We cannot capture light in a box. The word 'light' is not the name of anything, no more than the word 'time' is.

Every statement above is a remark about our concept 'light' -- or, in other words, about the grammar of the word 'light'. They are what Wittgenstein called "grammatical remarks" or "reminders".

Logic, metaphysics, natural sciences, and phenomena

It is not a something, but not a nothing either ... We have only rejected the grammar that tries to force itself on us here. (PI § 304)

But Wittgenstein is not suggesting that there is another kind of existence, but only pointing out that the grammar (part of speech) of name-of-object is not every noun's grammar. And his remark applies to the word 'light'.

Philosophy is not one of the natural sciences, and although metaphysical speculation about natural phenomena is possible (PI § 108) (despite Newton's rejection of "hypotheses"), logic (of language) does not seek to construct a theory about light, but instead to clarify our thinking about our common concept 'light'. (The most serviceable general definition of the word 'concept' is 'rules for using a word'.) Our investigation is not asking for facts about light but about our use of language. If logic (the word 'logic' so defined) is what we want from philosophy, then Wittgenstein's summary of our philosophical activity applies.

Philosophical investigations -- conceptual investigations ... (Z § 458)

Philosophy is not about constructing theories of reality but about clarifying thought. (TLP 4.112)

Enough of that. To return ... So there is a picture of the history of the stars millions of years ago -- i.e. a picture of the stars as they were millions of years ago only just reaching us today. Very well, one might say, but that picture has not shown us that the word 'light' is the name of some thing, and the stars are not film being run in front of a movie-projector bulb. Thus, this picture is only an object of comparison; it does not do the same service as the words 'velocity of light' (whatever that service actually is).

We must learn to think philosophically

The word 'light' is not a name-of-object word; that is not its part of speech. (The false grammatical account: "the essence of language is the putting together of names of objects.") If we recognize this, then we ought also to recognize the difficulties involved in talking about "the velocity of light". We must be wary of being savages who assume that we understand the conversations of civilized men (PI § 194).

The question is: why do we immediately assume that we understand when we are told: "This is a photograph taken this morning with a telescope; it shows us, not what was happening in Andromeda this morning, but what was happening there millions of years ago." And if we ask, How do you know? and are told "The distance to Andromeda and the speed of light", then we are satisfied. Why? [As school children we are taught to believe in the solar system.]

... only a very clever mind and a highly trained observer would have thought of it. But speculation remains speculation and should be labelled as such. It should not be put before a gullible public as the latest discovery of scientific certainty.

But why is the public "gullible" -- because by now almost all the public has been dragged through science classes at school? Why are we naive? Partly it is by training [the harm done by schooling], but partly it is from our language, the swiftness with which our imaginations can construct pictures from our language -- although the analogies we follow to construct the pictures are often, upon investigation shown to be, invalid.

We have to learn to think philosophically -- i.e. using the methods invented by the ancient Greeks and their disciples of the European Enlightenment. Philosophy is a thoughtful skepticism -- i.e. it is not simply doubt, but doubt with good reasons, i.e. with objective grounds for doubt that are conscientiously sought, because they are seldom obvious. We have to learn to think critically; and this is an area where there is truly "no end to learning".


Notes: "transparent white"

Runge says (in the letter that Goethe reproduced in his Theory of Colors), there are transparent and opaque colors. White is an opaque color. (Wittgenstein, Remarks on Color, tr. McAlister and Schättle, i, 17)

Light is the simplest, most undivided, most homogeneous element we know. It is not compounded. Least of all of colored lights. (quoted in Friedenthal, Goethe: his life and times (1963), p. 325; Goethe puts this at the head of his list of "experiences".)

... we may, for example, call lilac a "reddish-whitish-blue" ... but we cannot call white a "yellowish-reddish-greenish-blue" (or the like) And that is something that Newton didn't prove either. White is not a blend of colors in this sense. (Remarks on Color iii, 126)

... we speak of infra-red "light"; there is a good reason for doing it, but we can also call it a misuse [of the word 'light']. (ibid. iii, 127)

And when Newton shines a light source through a prism and says that light is composed of the colors that emerge from the prism, that could be called a misuse of the word 'composed'.

Goethe calls light an element, meaning that there is nothing simpler (a complex [a composition] can be broken into parts). However, is that how we use the word 'light'? I think it is. And why am I unable to say with certainty? For isn't 'light' a word I use everyday -- surely I am familiar with its usage. But here we are and we are not using the word 'light' in the familiar way; and it is not always clear whether we are talking about concepts (the use of a word) or about facts ("the world" as distinct from language).

... doesn't it seem obvious that the possibility of a language-game is conditioned by certain facts? (OC § 617b; cf. PI II, xii, p. 230a)

Well, obvious it may be -- but the exact way in which facts are related to our concepts (and to concept-formation) is nothing easy to say. [BACK]


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