by
the constant flux of things that he summed up his view of nature in the
words: "Everything flows"; of Empedocles, who found his explanation of
the world in the combination of the four elements, since become
traditional, earth, water, fire, and air; of Democritus, who developed
a materialistic atomism which reminds one strongly of the doctrine of
atoms as it has appeared in modern science; of Anaxagoras, who traced
the system of things to the setting in order of an infinite
multiplicity of different elements,--"seeds of things,"--which setting
in order was due to the activity of the finest of things, Mind.

It is a delight to discover the illuminating thoughts which came to the
minds of these men; and, on the other hand, it is amusing to see how
recklessly they launched themselves on boundless seas when they were
unprovided with chart and compass. They were like brilliant children,
who know little of the dangers of the great world, but are ready to
undertake anything. These philosophers regarded all knowledge as their
province, and did not despair of governing so great a realm. They were
ready to explain the whole world and everything in it. Of course, this
can only mean that they had little conception of how much there is to
explain, and of what is meant by scientific explanation.

It is characteristic of this series of philosophers that their
attention was directed very largely upon the external world. It was
natural that this should be so. Both in the history of the race and in
that of the individual, we find that the attention is seized first by
material things, and that it is long before a clear conception of the
mind and of its knowledge is arrived at. Observation precedes
reflection. When we come to think definitely about the mind, we are
all apt to make use of notions which we have derived from our
experience of external things. The very words we use to denote mental
operations are in many instances taken from this outer realm. We
"direct" the attention; we speak of "apprehension," of "conception," of
"intuition." Our knowledge is "clear" or "obscure"; an oration is
"brilliant"; an emotion is "sweet" or "bitter." What wonder that, as
we read over the fragments that have come down to us from the
Pre-Socratic philosophers, we should be struck by the fact that they
sometimes leave out altogether and sometimes touch lightly upon a
number of those things that we regard to-day as peculiarly within the