Tuesday, October 20, 2009

Richard Marshall Reviews "Seeing Dark Things: The Philosophy of Shadows" (Roy Sorensen)

This looks like a very interesting book - I have always been intrigued by shadows.

The Philosophy of Shadows

By Richard Marshall.


Roy Sorensen, Seeing Dark Things: The Philosophy of Shadows, OUP, 2008

This is a wonderful book, full of a profound, unsettling cleverness and weirdly satisfying counter-intuitiveness that the subject requires. Sorenson tries to answer puzzles that rear themselves in childhood and won’t be dispelled by the offhand disinterest of grown-ups. What is a shadow made of? (Absence of light.) What’s the difference between a shadow and a silhouette? (Silhouette’s are the far side of an object being shown on the side facing the observer and is therefore part of that object. A shadow is just an absence of light caused by an object blocking off light in a three dimensional space and so is no part of any object.) Is black a colour or just the absence of colour? (A colour.) Can you see darkness? (Yes, unless you’re blind.) Is there a difference between a blind person’s experience of a totally dark cave and a sighted person? (Yes, because dark is something that is seen, blindness is an absence of any seeing at all. Total dark is seen as black, if you can’t see you can’t see colour.) Do shadows spin if the object causing it spins? (Yes.) If you have two shadows and you join them side by side, do you still have two shadows? (Yes, although it may look to you that there is just one.) Can shadows move quicker than the speed of light? (Yes.)

He also asks other brilliant questions that are connected and analogous, such as questions about sound. Can you hear silence? (Yes, because silence is the total absence of sound and you pick that out by hearing. A deaf person can’t pick out anything by hearing.) Is there silence when there’s noise at the same time and in the same place? (No, because silence is the absence of noise. You can’t have absence of noise and noise at the same time and place. But there are interesting issues about where is a sound? Is it where it’s cause is, or everywhere the soundwaves go?) And he asks whether we see holes or just the surrounding things. Are holes things or just the shape of things? Or are they just gaps between things? (Holes are 3-D absent things, which is why we can see them and touch them and why don’t see the gaps between things as holes and can’t touch those gaps.) If there’s an eclipse of the sun caused by a large far planet getting in between us and the sun, and then a nearer smaller planet blocks out the far planet, which planet is blocking the sun from us, the near one or the far one? (This last one is Sorenson’s famous puzzle – he says you see the far one not the near one because it’s the far one that causes the blockage of light.)

Well, you can see from this list – and these are just some of his questions and answers, the guy asks more than this snap sample – that Sorenson is an amazingly fertile thinker. His conclusions are as unsettling as his questions, and the reasons he has for getting to the answers are also fantastic because they are rigorous and draw on up to date science and philosophy plus deft, quick-footed illustrations. He has a fantastic way of giving vivid thought experiments to get the strangeness of the whole subject across and there are loads of really helpful pictures too.

Sorenson has a reason for looking at shadows and such like. Sorenson takes issue with a prejudice against negative reality that he thinks colours much metaphysics and, because of this, science and semantics too. We are prejudiced against what is not there, favouring in our explanations what is present instead. He gives as examples of this prejudice Henri Bergson, Victor Hugo, Lewis Carroll and Jean Paul Sartre as all expressing this prejudice towards what is present over what is absent. He writes in his essay on Nothingness on the Stanford University website that; ‘Henri Bergson maintained that nothingness is precluded by the positive nature of reality. The absence of a female pope is not a brute fact. ‘There is not a female pope’ is made true by a positive fact such as the Catholic Church’s regulation that all priests be men and the practice of drawing popes from the priesthood. Once we have the positive facts and the notion of negation, we can derive all the negative facts. ‘There is nothing’ would be a contingent, negative fact. But then it would have to be grounded on some positive reality. That positive reality would ensure that there is something rather than nothing.’

Read the whole review.

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