the
prerequisites of knowledge--they are, in themselves, an essential part
of the knowledge of every cultivated person.

It is our task, not merely to show what these principles are, but to
point out how they have been discovered by our predecessors. We shall
trace the growth of these ideas from their first vague beginnings. We
shall see how vagueness of thought gave way to precision; how a general
truth, once grasped and formulated, was found to be a stepping-stone to
other truths. We shall see that there are no isolated facts, no
isolated principles, in nature; that each part of our story is linked
by indissoluble bands with that which goes before, and with that which
comes after. For the most part the discovery of this principle or that
in a given sequence is no accident. Galileo and Keppler must precede
Newton. Cuvier and Lyall must come before Darwin;--Which, after all, is
no more than saying that in our Temple of Science, as in any other piece
of architecture, the foundation must precede the superstructure.

We shall best understand our story of the growth of science if we think
of each new principle as a stepping-stone which must fit into its own
particular niche; and if we reflect that the entire structure of modern
civilization would be different from what it is, and less perfect than
it is, had not that particular stepping-stone been found and shaped and
placed in position. Taken as a whole, our stepping-stones lead us up and
up towards the alluring heights of an acropolis of knowledge, on which
stands the Temple of Modern Science. The story of the building of this
wonderful structure is in itself fascinating and beautiful.

I. PREHISTORIC SCIENCE

To speak of a prehistoric science may seem like a contradiction of
terms. The word prehistoric seems to imply barbarism, while science,
clearly enough, seems the outgrowth of civilization; but rightly
considered, there is no contradiction. For, on the one hand, man had
ceased to be a barbarian long before the beginning of what we call the
historical period; and, on the other hand, science, of a kind, is no
less a precursor and a cause of civilization than it is a consequent. To
get this clearly in mind, we must ask ourselves: What, then, is science?
The word runs glibly enough upon the tongue of our every-day speech, but
it is not often, perhaps, that they who use it habitually ask themselves
just what it means. Yet the answer is not difficult. A little at