Tuesday, 15 November 2011

The metre

Wittgenstein, in Philosophical Investigations, part 1, section 50, commented that we could not say that the standard metre bar in Paris was one metre long, nor that it was not one metre long. He went on to explain that this was not to ascribe some strange property to the metre bar, but only to note its peculiar role in the language game of measurement with the metre standard. Much has been written about the problem since. A good starting-point is the paper by W J Pollock, "Wittgenstein on The Standard Metre", Philosophical Investigations, 27:2, April 2004, available here:


Moving on to the modern definition of a metre as a certain fraction of the distance travelled by light in a second, we can reproduce the problem. One thing of which we cannot say either that it is, or that it is not, a metre is the distance travelled by any instance of a beam of light in vacuo in 1/299 792 458 of a second.

The philosophical analysis may be a bit different because the demonstrative referent (the referent of "that" in "that is what we mean by a metre") is not a physical object but a reproducible phenomenon, and one that is integrated with our physical theory. The words "any instance of" are included in order to separate examples from the theory, and get us as close as we can to actual metal bars. Our theory guarantees that it does not matter which instance we take.

Monday, 7 November 2011

Where was I before I was born?

Here is one of my favourite paragraphs, written by Angela Carter.

There's a theory, one I find persuasive, that the quest for knowledge is, at bottom, the search for the answer to the question: 'Where was I before I was born?' In the beginning was ... what? Perhaps, in the beginning, there was a curious room, a room like this one, crammed with wonders; and now the room and all it contains are forbidden you, although it was made just for you, had been prepared for you since time began, and you will spend all your life trying to remember it. ('Alice in Prague or The Curious Room', in Angela Carter, American Ghosts & Old World Wonders, London, Chatto & Windus, 1993, page 127.)

This could mean lots of things. The interpretation of the first sentence that most resonates with me is that each of us has a tremendous urge to merge his or her perspectival view of the world, the view from his or her own point of view, with a non-perspectival view from nowhere. Each perspectival view only endures for a lifespan. The non-perspectival view is in principle available at any time and the same for all, although different people would interpret what they saw differently, but that view is in practice available to no-one. To see the world as it was before I was born, or as it will be after I die, I would have to be somewhere at a time when I was not, or will not be. There would have to be a place I was before I was born, and a place I would be after death. What I can in fact do is see traces left by the past, and current indications of what the future might hold, and make inferences from those traces and indications. But that is not the same thing at all.