e astronomer. The efficacy of a
serum in the cure of diseases may convince him that work done in the
laboratory is not labor lost.

It seems evident that the several sciences do really rise on stepping
stones of their dead selves, and that those selves of the past are
really dead and superseded. Who would now think of going back for his
science to Plato's "Timaeus," or would accept the description of the
physical world contained in the works of Aristotle? What chemist or
physicist need busy himself with the doctrine of atoms and their
clashings presented in the magnificent poem of Lucretius? Who can
forbear a smile--a sympathetic one--when he turns over the pages of
Augustine's "City of God," and sees what sort of a world this
remarkable man believed himself to inhabit?

It is the historic and human interest that carries us back to these
things. We say: What ingenuity! what a happy guess! how well that was
reasoned in the light of what was actually known about the world in
those days! But we never forget that what compels our admiration does
so because it makes us realize that we stand in the presence of a great
mind, and not because it is a foundation-stone in the great edifice
which science has erected.

But it is not so in philosophy. It is not possible to regard the
philosophical reflections of Plato and of Aristotle as superseded in
the same sense in which we may so regard their science. The reason for
this lies in the difference between scientific thought and reflective
thought.

The two have been contrasted in Chapter II of this volume. It was
there pointed out that the sort of thinking demanded in the special
sciences is not so very different from that with which we are all
familiar in common life. Science is more accurate and systematic, it
has a broader outlook, and it is free from the imperfections which
vitiate the uncritical and fragmentary knowledge which experience of
the world yields the unscientific. But, after all, the world is much
the same sort of a world to the man of science and to his uncritical
neighbor. The latter can, as we have seen, understand what, in
general, the former is doing, and can appropriate many of his results.

On the other hand, it often happens that the man who has not, with
pains and labor, learned to reflect, cannot even see that the
philosopher has a genuine problem before him. Thus, the plain man
accepts the fact that he has a mind and that it knows the wo