Friday, June 1, 2012
Color holds and quantum theory
When figuring out how many human beings of average weight can be carried on an airplane, engineers deal with abstractions. For one thing, they ignore every aspect of actual, concrete human beings except their weight; for another, they ignore even their actual weight, since it could in principle turn out that there is no specific human being who has exactly whatever the average weight turns out to be. This is perfectly fine for the specific purposes at hand, though of course it would be ludicrous for those responsible for planning the flight entertainment or meals to rely solely on the considerations the engineers are concerned with. It would be even more ludicrous for them to insist that unless evidence of meal and movie preferences can be gleaned from the engineers’ data, there just is no fact of the matter about what meals and movies actual human beings would prefer.
Now as I’ve emphasized in a couple of recent posts (here and here) the description of the world physics gives us is no less abstract. Physics simply does not give us material systems in all their concrete reality; it focuses only on those aspects of a system that are susceptible of prediction and control, and thus on those aspects which can be modeled mathematically. Hence there is no reason whatsoever to think that if the description physics gives us of some particular system does not include a reference to some cause, it follows that there is no cause -- especially since (as Bertrand Russell emphasized) it is arguable that causality of any sort is, strictly speaking, left out of the description of the world that physics gives us.
Here is a (perhaps odd but I think useful) analogy to illustrate the relationship between concrete reality and the abstract description provided by physics. The artwork you see on the page of a comic book is typically produced in three stages. First, the main outlines of the illustrations are laid out in pencil. Second, an inker goes over the pencil work in black ink, and sometimes (especially if the penciller and the inker are the same artist) it is at this stage that the fine details of the illustrations are added. In the normal case it is only inked work that is ready for publication; pencils alone do not reproduce as well, and drawings made in blue pencil will not reproduce at all by normal methods. Third, the color is added, often by a separate artist. In the old days this was done by using watercolors on Photostats of the inked artwork, which would serve as a guide for the printer. These days it is typically done using computer software.
Now, for the most part the contours of an image are rendered in ink, as are shadows and other lighting effects (e.g. those associated with explosions). The colors merely fill in the space within the contours of an inked image. But there is a technique, known as a “color hold,” by which some of the contours of an image or some lighting effects are laid down at the coloring stage. The pencil artist might give indications (in blue pencil, say) of what the contours or effects should look like, but these are not inked and would not show up if the inked artwork was reproduced without color.
So, consider for example Harvey Kurtzman’s cover for Two-Fisted Tales #21, which shows an army jeep being blasted into the air by a land mine. The explosion itself and much of the shadow on the part of the jeep visible to us was added at the coloring stage and is at best only vaguely indicated in the uncolored inked artwork. Or consider Bernard Krigstein’s striking cover for Piracy #6, which portrays a dejected castaway drifting in a small boat under an oppressively hot sun. Both the wave on which the boat sits and the sun and the rest of the sky are almost entirely represented in color alone. Only the castaway, the boat, and the boat’s shadow on the water are rendered in ink.
Now, in each of these cases it is only what appears on the published cover that counts as a complete image. The inked artwork by itself might be regarded as a kind of abstraction from the complete image. It captures much of what is there in the complete image, but not the whole of it. Obviously it does not capture the color. But it does not even capture every aspect of a certain type. For instance, it doesn’t capture even every solid object (as opposed to the light falling on solid objects) -- in the second image, it captures the boat and the castaway, but not the wave -- and it does not capture all the shadows -- in the first image, it captures only part of the shadow cast by the explosion on the jeep, not all of it. Nor does it capture every aspect of the causality represented by the completed image. For example, in the first image the inked artwork alone represents the jeep’s being in the air, but it does not clearly represent the explosion as the cause of the jeep’s motion; only the completed, colored image represents that clearly. In the second image, the inked image alone represents the castaway lying within the boat, but it does not clearly represent the boat being held up by a wave; only the completed, colored image conveys that. (Had the coloring been done differently, we can even imagine it representing instead the boat sitting atop some rocks, or falling from the sky into the water.)
Obviously, then, it would be a mistake for someone to conclude from the inked artwork alone that the first image represents a jeep floating in the air without a cause, or that the second image represents a man lying in a boat which is not being held aloft by anything. The causal factors in question are absent from the inked images, but it does not follow that the inked images represent their absence. Rather, the inked images are by themselves incomplete; the causal factors in question are to be found only in the completed artwork.
Similarly, and as I have noted before, it is a fallacy to infer from the absence of such-and-such a causal factor in quantum theory’s description of some physical system (the hydrogen atom, say) the conclusion that quantum theory shows that such-and-such a causal factor is absent in objective physical reality. For quantum theory, like other theories in physics, does not give us a complete description of concrete physical reality in the first place. Nor does it necessarily give us a complete description even of a particular aspect of physical reality (such as causation). It can lead us to ask interesting questions about those aspects of physical reality it doesn’t capture, just as a piece of black and white inked artwork can lead us to ask interesting questions about what the completed image is supposed to look like. (What is the boat supposed to be resting on? What sort of causal factors underlie the transition of the electron to a higher energy level?) But physics alone cannot in principle provide all of the answers to those questions.
You might say that physical science sees the world as if it were a piece of black and white artwork. What it has to tell us is true, but it is not the whole truth, and to treat it as if it were threatens severely to distort our perception of reality. To see the natural world in all of its rich, colored variety you need philosophy, and in particular the philosophy of nature.