e to exhibit the
form of nexus between these physical antecedents and ideas. Even if the
knowledge of the topography of the brain were immeasurably more advanced
than it now is, even though we could observe the vast network of
nerve-fibres and filaments of which the brain is composed, and could
discern the actual changes in brain-cells under nerve stimulations, we
should still be a long way off from understanding the nature and genesis
of ideas which can only be known to us as immediate in their own quality.
All that we can ever affirm is that a certain physical excitation is the
antecedent of thought. It is illegitimate to say that it is the 'cause'
of thought; unless, indeed, the word 'cause' be invested with no other
meaning than that which is involved in such a conception. It is,
however, in a very general way only, and within an exceedingly narrow
range, that such measurement is possible. We do not even know at present
what nerves correspond to the sensations of heat and cold, pain and joy;
and all attempts to localise will-centres have proved unavailing.

The finer and more delicate feelings cannot be gauged. But even though
the alleged parallelism were entirely demonstrated, the immediate and
pertinent question would still remain, Who or what is the investigator?
Is it an ego, a thinking self? or is it only a complex of vibrations or
mechanical impressions bound together in a particular body which, for
convenience, is called an ego? Are the so-called entities--personality,
consciousness, self--but symbols, as Professor Mach says, useful in so
far as they help us to express our physical sensations, but which with
further research must be pronounced illusions?[1] Monistic naturalism,
which would explain all psychical experiences in terms of cerebral
action, must not be allowed to arrogate to itself powers which it does
not possess, and quietly brush {86} aside facts which do not fit into its
system. The moral sanctions so universally and deeply rooted in the
consciousness of mankind, the feelings of responsibility, of guilt and
regret; the soul's fidelities and heroisms, its hopes and fears, its aims
and ideals--the poetry, art, and religion that have made man what he is,
all that has contributed to the uplifting of the world--are, to say the
least, unaccounted for, if it must be held that 'man is born in chains.'
Primary facts must not be surrendered nor ultimate experiences sacrificed
in the interests of t