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"... What is meant by a true and natural class? [...] my opinion is that it
is a shallow and sciolistic metaphysics which declares a "real class," in
the sense which those writers attach to the term, to be an impossible thing.
At the same time, I am unable to see any need at all in positive science for
considering such metaphysically real classes. To my apprehension the
business of classification has no concern with them, but only with true and
natural classes, in another and a purely experien