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Starlight - Messages from the Past?

What is light? Models that describe the behavior of light, whether as particle, wave, or as now one, now the other, are scientific theories -- they are abstractions, not replacements for the reality before our eyes. There are two broad kinds of definition (conventions and hypotheses), and it's essential to be clear about which kind we are looking for in philosophy; as it is important to know the difference between a theory and a statement of fact.

M. O'C. Drury pointed out that the word 'light' is not the name of some thing, and that the meaning of 'velocity of light' is not the velocity of some thing. (A note about the word 'thing'.)

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" (PI § 383)), although the roles of nouns are most varied. When even "abstract terms" are assumed to be names, they seem to give us some thing to hold onto, even if there is nothing there. For example, "What are numbers?"

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)

Drury is saying two things. (1) If you don't know how the results are derived, then you don't understand the results. And (2) that light is light, uniquely itself -- and not some other thing.

I want to say that every time you open your eyes a miracle occurs. (DW p. 73)

At school we were required to understand -- or pretend to understand -- in order to pass exams -- the meaning of such marks on paper or spoken sounds as 'speed of light', 'photon', 'light wave'. Doing well on the exam -- that was the criterion for saying that someone 'understood' or 'did not understand' (understanding is a public event). We learned to play a game (cf. "language game" i.e. an activity with language following more or less strict rules). And don't imagine that a move in a game cannot be nonsense, because nonsense is what children have been taught about the word 'point' in geometry for thousands of years ("A geometric point is an object without extension". That nonsense is similar to the examples George Berkeley gives: 'velocity without motion' and 'motion without extension').

"The word 'light' is the name of some thing." What those words suggest is a picture, e.g. 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 back 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 don't know how to compare a picture with what it is a picture of, then the picture is mere fantasy (imagination, metaphysics). The question is always: How do you verify that?

"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 already happened, weeks, months, ago.

And so we imagine it works the same way with light from the stars: the thing named 'light' carries information to our eyes [as if it were a newspaper photograph] about of what happened millions of years ago. But in what sense can light, which is not a thing, "carry" anything? What might that expression mean?

Albert Einstein said that he imagined himself traveling on "a beam of light", as if light were something you could sit on like a trolley car. And we can also picture light as a series of photons or as a wave. And such pictures may be consistent with selected facts, but they are not the fact [light] itself. Those pictures should not be confused with pictures of light; there are no pictures of light.

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

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

The word 'force' is without 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 is 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. If the word 'light' is not the name of an object (and if as a phenomenon light is nebulous), then what is 186,000 miles/second the speed of?

M. O'C. Drury wrote ("Fact and Hypothesis" (p. 137)) that a very high degree of skill and instrumentation was necessary to form an hypothesis and devise an experiment to test that hypothesis. 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 and waves. But "the experiments reveal no such entities". (Particles and waves are scientific models of light; but they are not light.)

And in this way Drury says that "Light is light, neither particle nor wave", that photons and waves are creations of the imagination. Everything is what it is, and not really something else: Light is not really particle or wave. If we do not understand the nature of a scientific theory, namely that a theory is a creatively organized selection of facts (i.e. facts plus imagination), and that therefore a theory cannot be a substitute for reality, then --

Reality which lies before us at every moment is replaced by the abstract picture we have ourselves created. (DW p. 100)

Compare 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). Here imagination allows a theoretical invention to replace the solid table that stands in front of us. But the table is the reality; atoms and space is the theory.

"What is light -- really?" As if the question for philosophy were Platonic: What is the essence of light? rather than logic of language: What is the use of the word 'light' in the language?

"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 (which may be nothing). Question: Are the pictures this language suggests the meaning of the hypothesis?

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. (PI II, iv, p. 178)

Andromeda snaps: "... in Andromeda I am really seeing something that was contemporary with millions of years ago." The difficulty is not to invent pictures to give a sense to those words, but to say what relation, if any, those pictures have to reality.

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. But what thing is the beam a beam of? Is the word 'light' the name of that thing? But a flashlight only casts light a short distance. But if light is a thing, then why does it stop, and where does it go when it reaches the limit of the beam?

Then is 'light' 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' the name of a thing? Is that how we use that word?]

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? If the universe is round, like the soap bubble picture ("The universe is finite but unbounded"), then we can make the observation ourselves: we position 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 pictures is not the difficulty. But does such a picture do the same service (PI II, iv, p. 178) as the words 'the velocity of light' does?

Now, imagine that we set up two motion-picture screens, one in front of a 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 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.

Definitions and phenomena

Comparison to sound. The Greeks noted that from the mountainside you see the oars strike the water before you hear the splash. From which is said to follow the conclusion: "Therefore light is faster than sound." But that conclusion is nonsense unless it simply means that you see some things before you hear them. We are talking about our concept 'light' and therefore the use of a word.

[Note in margin: Only it is possible to be interested in a phenomenon in a variety of ways]. (PI § 108)

There is the use of word 'light', and there are scientific theories about light. As we normally use the word 'light' is not the name of a thing that carries images to our eyes. (Compare "definitions": definition of the word 'thunder' versus definitions of -- i.e. hypotheses about -- thunder.) It is also possible to write about light from the point of view of the philosophy of science, as Drury does, or of metaphysics, as Boethius does (The carrier picture -- eidolon -- of light is his).

"What color is Light?"

"White is not the only color of light." On the contrary, white is not the color of any light. Light is "clear as glass" as it were; were it opaque it would not allow us to see anything but itself; as Wittgenstein wrote, there is nothing we call 'transparent white' [Note]. If we pass the light from a source through colored glass or through a prism we see what we call "colored light". That however is not equivalent to saying that a prism "divides white light into its component colors", because the combination of colored lights is not white -- i.e. clear -- light.

Are the remarks above statements of fact or rules of grammar (Are they remarks about our concept 'light', or in other words, about the grammar (in Wittgenstein's jargon) of the word 'light')? They are what Wittgenstein called "grammatical remarks" or "reminders" -- why? Because that is the work they are used to do here. It is our concept 'light' (our use of a word) that I want to make clear (first of all to myself).

The following are statements of fact, not rules of grammar (i.e. not semantically defining: their negation is not nonsense). Sound does not pass through a vacuum; light does. Light does not pass through walls; sound does. Where there is nothing to illuminate, there is no light.

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 if 'light' is not the name of something, then it is the name of nothing, and how can there be a velocity of nothing?" But Wittgenstein is not suggesting that there is another kind of existence ("something-nothing"), but only pointing out that the grammar (part of speech) of name of object is not the grammar of every noun. And his remark applies to the word 'light'.

Note: the word 'thing' is our language's broadest category. "A noun is the name of a person, place, or -- anything at all." Everything is something ("some thing"), including ghosts, numbers, unicorns, space, light, time, points, and so on. (Cf. the word 'phenomenon'.) But in this sense, 'thing' ≠ 'object' or 'entity'.

Wittgenstein's Philosophy

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 the concept 'light'. [The most serviceable, in my view, general definition of the word 'concept' is 'rules for the use of a word'.] Our investigation is not asking for facts about light but about our use of language [although our use of language = our concepts is intertwined with very general facts of nature]. If logic (the word 'logic' so defined) rather than speculation (metaphysics), 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. (cf. TLP 4.112)

Enough of that. To return ... So we have drawn a picture of the stars as they were millions of years ago only just reaching us today, carried by light at the speed of light. But in that picture the word 'light' is the name of a carrier [trolley car], a thing named 'light'. Which means that the picture is not a picture of our normal use of the word 'light'; the picture is a misrepresentation of that use (PI §§ 425-426).

We must learn to think philosophically

The word 'light' is not a word that names an object; that is not its part of speech. (The false grammatical account: "the essence of language is the putting together of names of objects, whether tangible or abstract.") If we recognize this, then we ought also to recognize the difficulties involved in talking about "the velocity of light" (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? How is this verified? 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.]

"... of millions of years ago" is an hypothesis -- but is it an hypothesis that can be falsified? How?

... only a very clever mind and a highly trained observer would have thought of it. But speculation remains speculation and should be labeled 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 natural science classes at school? Why are we naive? Partly it is from the harm done by schooling, but partly it is from our language, namely the swiftness with which our imaginations construct pictures from our language -- although the analogies we follow to construct the pictures often, upon investigation, are shown to be misrepresentations of the grammar -- i.e. use according to rules -- of our language. And partly it is because we have to learn to think philosophically.

Getting hold of the difficulty deep down is what is difficult.... One doesn't put the question marks deep enough down. (CV p. 48, 62)

Philosophy is a thoughtful skepticism -- it is grounds for doubt that are conscientiously sought, because they are not obvious.

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 then it is said 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? 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 a concept (the use of a word) or about facts of nature and hypotheses in contrast to language.

Between facts and grammar

If the formation of concepts can be explained by facts of nature, should we not be interested, not in grammar, but rather in that in nature which is the basis of grammar?

Our interest certainly includes the correspondence between concepts and very general facts of nature.

I am not saying: if such-and-such facts of nature were different people would have different concepts (in the sense of a hypothesis). But: if [we] imagine certain very general facts of nature to be different from what we are used to, [then] the formation of concepts different from the usual ones will become intelligible to [us]. (PI II, xii, p. 230)

... doesn't it seem obvious that the possibility of a language game is conditioned by certain facts? (OC § 617)

In some cases it does seem obvious -- Wittgenstein gives the example of weighing cheese on a scale (PI § 142). But the exact way in which facts are related to our concepts (and to concept-formation) is not always easy to say. For example, many concepts are made of uncompelling so-called family resemblances, similarities which are merely myriad.

It seems that the everyday concept 'light' is defined ostensively in the presence of light rather than verbally ("Put out the light" and "It's dark in here", and language games like these learned in childhood), but then scientists have a say in this and it becomes accepted to speak of "infra-red light" and "light beyond the visible spectrum" or in other words "invisible light"; so that scientists have extended the everyday concept 'light' to include an hypothesis (a classification system that may later be abandoned). [BACK]

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