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Error of Descartes

  1. Jun 28, 2003 #1
    Descartes believed that space without matter did not exist. "If that which is in a hollow vessel were taken out of it without anything entering to fill its place, the sides of the vessel, having nothing between them, would be in contact."
    "The nature of matter . . . does not consist in a thing being hard, or heavy, or coloured, but only in its being extended in length, breadth and depth."
    What arguments do we use today to show that this concept is wrong? What is space without matter? What is the commonly accepted concept of matter?
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  3. Jun 28, 2003 #2

    Tom Mattson

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    I think Descartes is right. Space without matter and time without motion are empty concepts. Today, our best theory of spacetime is GR, in which the geometry of spacetime is completely determined by the distrubution of matter (by that I mean all energy-momentum density) in the universe.

    No matter in motion-->No spacetime.
  4. Jun 28, 2003 #3
    That's unexpected, I suppose. The question came from Maxwell's Matter and Motion (which is a very good book by the way), Article 16. Maxwell makes it very clear that he finds Descartes' assumption to be false. Thus, he titles the Article "Error of Descartes." I gave my confidence to Maxwell, since he was a more modern thinker. He was before Einstein, however, so it shouldn't surprise me that some of his ideas are wrong.
  5. Jun 28, 2003 #4

    Tom Mattson

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    I wouldn't say "wrong", as this is a philosophical (as opposed to scientific) question. In other words, it can't be settled experimentally.

    One view of space is that of Newton, who held that space and time are absolute, independent of moving bodies. The other is that of Leibniz, who held that space and time are relational, existing only as concepts--modes of existence of moving matter.

    It seems that Maxwell has chosen to side with Mr. Newton. The conceptual problem I have with the absolute picture of space arises when putting it to the extreme test: trying to imagine space with no matter in it. What does "1 meter of space" look like? How can you even tell? In your mind's eye, you might try to envision a meter stick imposed on the blackness to measure space, but introducing a meter stick is not allowed, because that is a material body! The same goes for time: How would I measure time with just empty space and no motion? Answer: I can't. Thus, I agree with the relationalists that space and time are meaningless outside the context of moving matter.
  6. Jun 28, 2003 #5
    I think this can't be done. Because the walls of the vessel must consist of physical objects, and these will interact with each other.

    I think Descartes made this assumption because of the mechanistic concept that was standard those days.
  7. Jun 28, 2003 #6
    There is a difference between empty space and nothingness. Empty space has physical properties (e.g. vacuum energy, permitivitty, etc). Nothingness does not.

    In my opinion there were only two decent philosophers from the modern genre... Descartes and Kant.


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