dead matter. The argument from the
existence of mnemic phenomena in physiology must therefore be allowed a
certain weight against the hypothesis that mnemic causation is ultimate.

* See his "The New Physiology and Other Addresses," Griffin,
1919, also the symposium, "Are Physical, Biological and
Psychological Categories Irreducible?" in "Life and Finite
Individuality," edited for the Aristotelian Society, with an
Introduction. By H. Wildon Carr, Williams & Norgate, 1918.

The argument from the connection of brain-lesions with loss of memory is
not so strong as it looks, though it has also, some weight. What we
know is that memory, and mnemic phenomena generally, can be disturbed or
destroyed by changes in the brain. This certainly proves that the brain
plays an essential part in the causation of memory, but does not prove
that a certain state of the brain is, by itself, a sufficient condition
for the existence of memory. Yet it is this last that has to be proved.
The theory of the engram, or any similar theory, has to maintain that,
given a body and brain in a suitable state, a man will have a certain
memory, without the need of any further conditions. What is known,
however, is only that he will not have memories if his body and brain
are not in a suitable state. That is to say, the appropriate state
of body and brain is proved to be necessary for memory, but not to be
sufficient. So far, therefore, as our definite knowledge goes, memory
may require for its causation a past occurrence as well as a certain
present state of the brain.

In order to prove conclusively that mnemic phenomena arise whenever
certain physiological conditions are fulfilled, we ought to be able
actually to see differences between the brain of a man who speaks
English and that of a man who speaks French, between the brain of a man
who has seen New York and can recall it, and that of a man who has never
seen that city. It may be that the time will come when this will be
possible, but at present we are very far removed from it. At present,
there is, so far as I am aware, no good evidence that every difference
between the knowledge possessed by A and that possessed by B is
paralleled by some difference in their brains. We may believe that
this is the case, but if we do, our belief is based upon analogies
and general scientific maxims, not upon any foundation of detailed
observation. I am myself inclined, as a working hypot