VIII
THE RELATION OF SENSE-DATA
TO PHYSICS
I. THE PROBLEM STATEDtop
PHYSICS is said to be an empirical science, based upon observation and experiment.
It is supposed to be verifiable, i.e. capable of calculating beforehand results subsequently confirmed by observation and experiment.
What can we learn by observation and experiment?
Nothing, so far as physics is concerned, except immediate data of sense: certain patches of colour, sounds, tastes, smells, etc., with certain spatio-temporal relations.
The supposed contents of the physical world are prima facie very different from these: molecules have no colour, atoms make no noise, electrons have no taste, and corpuscles do not even smell.
If such objects are to be verified, it must be solely through their relation to sense-data: they must have some kind of correlation with sense-data, and must be verifiable through their correlation alone.
But how is the correlation itself ascertained? A correlation can only be ascertained empirically by the correlated objects being constantly found together. But in our case, only one term of the correlation, namely, the sensible term, is ever found: the other term seems essen-
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