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337
HERMANN VON HELMHOLTZ
with the possibility and the legitimacy of all natural know-
ledge. The heavens and the earth doubtless exist apart from
ourselves, but for us they only exist in so far as we perceive
them. Part of what we perceive therefore appertains to our-
selves part only has its origin in the properties of the heavens
and the earth. How are we to separate the two? Helm-
holtz's physiological investigations have cleared the ground for
the answering of this question: they have supplied a firm
fulcrum to which a lever can be applied. His own inclina-
tions have led him to discuss these very questions in a series
of philosophical papers, and no more competent judge could
express an opinion upon them. Will his philosophical views
continue to be esteemed as a possession for all time? We
should not forget that we have here passed beyond the
bounds of the exact sciences: no appeal to nature is possible,
and we have nothing but opinion against opinion and view
against view.
As on the one hand Helmholtz was led by the study of
the senses to the ultimate sources of knowledge, so on the
other hand the same study led him to the glories of art.
The rules which the painter and the musician instinctively
observe were for the first time recognised as necessary con-
sequences of our organisation, and were thereby transformed
into conscious laws of artistic creation.
Great and manifold as are these discoveries, they are all
eclipsed by another with which the name of Helmholtz will
ever be connected. This is a physical discovery of a more
abstract nature. Here the human observer with his sensations
retires into the background: light and colour fade away and
sound becomes fainter; their place is taken by geometrical
intuitions and general ideas, time, space, matter, and motion.
Between these ideas relations have to be found, and these
relations must correspond to the relations between the things.
The value of these relations is measured by their generality.
As relations of the most general nature we may mention
the conservation of matter, the inertia of matter, the mutual
attraction of all matter. Of new relations discovered in this
century the most general is that which was first clearly
recognised by Helmholtz. It is the law which he called the
Principle of the Conservation of Force, but which is now
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