argued that the atom of matter is an energy unit, while
the discoveries concerning radio-activity both argue for
the breaking down of the supposedly ultimate dis-
tinctions of substance between the chemical elements,
and seem to show that all atoms are really units of
electrical energy.³ But whatever the details of definition
of the ultimate physical element, the most serious
students of mathematical physics and chemistry no
longer admit any such thing as philosophers and the
common run of men suppose that they mean by matter;
--in fact, by philosophers frequently written 'Matter.'
Indeed, as I understand it, the only capital-letter
Materialists to-day, the only educated persons who are
still able at all to conceive of the little tennis-balls, are
the idealistic philosophers. These considerations are not
urged, however, as an argumentum ad homines, save in
so far as it is logically sound to draw one's opinions on
any topic from the persons who by reason of special
study are qualified to pronounce. In our present
case the only persons qualified are the very ones
who would naturally be prejudiced in favour of
the strictly 'material' as opposed to the conceptual or
neutral.

Now these very persons, to leave physics for meta-
physics, may perhaps be the last to admit that an
electron is a concept. "Not a concept," they will say,
"but a real thing" ;--as if this were an antithesis.
Physicists, however, while some of them are experts
in the analysis of matter, are not so well qualified to give
verdict as to the nature of reality and of concepts. As
the botanist analyses the structures of vegetable
organisms and finds the chemical compounds of which
they are built, but does not analyse them; so the

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