| | Nathan,
Space is actually a kind of relationship between objects. In order to measure the distance between two things, one must have two things to measure the distance between. As such, there is no way to measure space independently of a material object. So you're right in saying that we can only measure space (and motion) in terms of material objects and time.
Also, know that the objection of reality being unknowable due to its 'continuity' is precisely the main issue that Rand addresses in her discussion "Exact Measurement and Continuity."
In short, I think I agree with you, but I'm not sure since some of the terms you use make me nervous.
Daniel,
Firstly, I've tried to illustrate that what Ayn Rand calls "exact" or "absolutely precise" everyone else calls "approximate" etc. and that this is likely to be misleading, as she has no better solution to the problem of precision other than swapping the words around (you may call this being more "philosophical" if you like!). I believe I have done this. Yes, I agree with Ed here, that Rand (of all people) knew better than to throw around the term "absolute" too cavalierly. In that sense, it was a poor word choice, since absolute means "irrespective of context," when Rand's entire solution to the problem of measurement is to recognize that measurement is contextual.
This then led to a discussion of the above problem, in which I hoped to highlight the very interesting difference between *abstract standards* and physical ones. Because "centimetre" is merely shorthand for the following formula: "1/100th of the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second". This formulation is of course, an *abstract* standard: that is, a *conscious methodological decision* formulated in *words and numbers*. You bring up an interesting point here, since I've largely discussed units which are at the perceptual level (i.e., blocks and rods). The question of instruments acting as intermediates never occurred to me. However, you're right that you need some kind of instrument to determine the length of a meter this way. This gets into the special sciences with which I'm unfamiliar.
However, I do know that one must calibrate one's instruments either at the perceptual level or in terms of other, lower level instruments which have been similarly calibrated, to bring them in terms of the perceptual level. This is something akin to what Galileo did with his telescope to be sure that it wasn't tricking him: he observed distant objects through it, and then walked to those objects and verified that they did indeed match what his senses observed.
If we keep discussing in this vein, we may eventually uncover issues in the Realism vs. Instrumentalism debate in the Philosophy of Science.
Now, we can try to *approximate* the standard set by this formulation, and can do so remarkably precisely - but not *absolutely*. This is because, obviously, the length of the path the light travels is in the first place *measured by an instrument* (a physical ruler), and similarly the time taken to travel it is *measured by an instrument* (a physical clock).
Again, I'm not sure how scientists go about making copies of metersticks by this method-- it would be interesting to find out, actually. However, there has to something akin to the 1,000,000 units vs. km test I've written about before to be sure that the meterstick is a valid measuring tool in the context for which it was created.
I'm glad you've written this last post, since it presents your views very nicely. It has helped clarify this issue that we've bounced around in the last few posts:
Of course I do not subscribe to Rand's theory of concepts, but I must say this comment makes me curious. How then? Concepts, as defined by Rand, are mental integrations of existents which have some similar characteristic. Its purpose is to allow one to recognize a certain kind of existent and to categorize one's knowledge abstractly, instead of storing one's knowledge as facts about concretes. As such, a concept is a mental entity, not a material one, and therefore it cannot be measured in units of length, as it has no material extension. It would be like trying to measure mass in inches-- it cannot be measured in that way.
However, I think by "concept of centimeter," you are referring to the "abstract standard" of the light-based definition of the meter, is that right?
Nate T.
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