EVOLUTION OF MIND 235

evolution has made some strides; it is always dependent
on the development of the nervous system. This is
an inference from the facts of individual development
and racial evolution, which clearly show that mental
life emerges from antecedent stages in which only
bodily life can be discerned. And if mental life were
a merely incidental quality, like the possession of red
blood, there would be no objection to the inference.
But since mental life is almost from the first a
necessary postulate—wherever we have to deal with
behaviour—and as we are quite unable to suggest
how it can arise out of metabolism, it seems more
scientific, at present, to regard the potentiality of mind
as being just as primitive as metabolism. It should
be noted that the most recent researchesI on the
behaviour of the simplest animals disclose something
more than reflex actions, namely a pursuit of the
method of trial and error, involving some of the
fundamental qualities seen in higher animals.

Just as inorganic evolution must have made many
advances before organisms became possible, so organic
evolution must have made many advances before the
mental side of life could find distinct expression. But
as we cannot retranslate the daily activities of even a
very simple animal into chemico-physical language,
we are forced at present to conclude that what is
called inanimate matter has somehow wrapped up
with it the potentiality of life; and as we cannot re-
translate behaviour into the metabolism of nerve-cells,
we are forced at present to conclude that life has
somehow wrapped up with it the potentiality of mind.

1H. S. Jennings," Publications of Carnegie Institute/'Washington,
No. 16 (1904), pp. 1-256.ited into aggregates