Tuesday, October 16, 2012

Are Space and Time Real?

We humans are born, live, and die, and experience ourselves moving through time.  We open our eyes and see objects before us.  It seems sensible to see space as a container, as Plato did, and time as the flow of a river.  But are they real?  Can we speak as Newton did of absolute space and time?

The early modern era brought these questions into sharp relief, and by the time that Kant came along there were several contesting notions abroad, from Newton's absolute space and time--though he insisted that humans could only experience relative space and time--to Bishop Berkeley's idealist notion that we cannot experience absolute space and time and so should content ourselves with experiencing sensible things.  For Hume, impressions come before ideas, so space is our interpretation of a bundle of impressions that seems to suggest extension.

Kant's Big Idea is to drive his ship between the Scylla of absolute space and time and the Charybdis of external impressions.  He doesn't want to prejudge the world as real, for Berkeley shows that our ideas of the world are all in the mind.  But he doesn't want to concede to Hume that the world imprints itself upon us.  Thus for him space and time are forms of intuition independent of experience.  They form a mental framework, forms of intuition, that the mind uses to make sense of sensible impressions.  Says he:
By means of outer sense [i.e. physical sensations of external objects]... we represent objects as outside us, and all as in space.
But he argues that the "representation of space" can't be obtained from experience but rather that "outer experience is itself possible only through this representation."  We do not get our experience from outside; we manufacture it inside us, and only then apply it to the outside world.

This is a theme that repeats itself again and again in Kant, and you can see that it comes down to us in current notions of the way that science works.  You have a problem, so you gather some data.  Then you come up with a theory in your mind, a mental idea of how the world works.  You test it against the data.  If it works, your mental idea is your new view of the world.  Until your wonderful theory crashes and burns and another theory comes up and supersedes it.

Now Kant does not consider space as an illusion, existing only in the mind.  He argues the reality of space for "everything that comes before us externally as an object."  But he insists on the "transcendental ideality" of space when we are talking about things in themselves.

When it comes to time, Kant asserts that "time is nothing other than the form of inner sense, i.e., of the intuition of our self and our inner state."  And it is a necessary condition of our experience of space as well, because we could not experience external objects unless they were experienced in time.

Again, Kant asserts the "empirical reality of time" an an objective reality of all "objects that may ever be given to our senses."  But not "absolute time". That "transcendental ideality" could "never be given to us through the senses."

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