everyday work of seeking food and building huts and carrying on warfare,
and yet even he found time to classify the objects of his world and to
construct some theory about the powers that made them. His attainments may
seem crude and childish to-day, but they were the beginnings of classified
knowledge, which advanced or stood still as men found more or less time
for observation and thought. Freed from the strife of primeval and
medieval life, more and more observers and thinkers have enlarged the
boundaries and developed the territory of the known. The history of human
thought itself demonstrates an evolution which began with the savages'
vague interpretation of the "what" and the "why" of the universe, and
culminates in the science of to-day.

What, now, is a science? To many people the word denotes something cold
and unfeeling and rigid, or something that is somehow apart from daily
life and antagonistic to freedom of thought. But this is far from being
true. Karl Pearson defines science as _organized knowledge_, and Huxley
calls it _organized common sense_. These definitions mean the same thing.
They mean that in order to know anything that deserves confidence, in
order to obtain a real result, it is necessary in the first place to
establish the reality of facts and to discriminate between the true, the
not so sure, the merely possible, and the false. Having accurate and
verified data, scientific method then proceeds to classify them, and this
is the _organizing_ of knowledge. The final process involves a summary of
the facts and their relations by some simple expression or formula. A good
illustration of a scientific principle is the natural law of gravitation.
It states simply that two bodies of matter attract one another directly in
proportion to their mass, and inversely in proportion to the square of the
distance between them. In this concise rule are described the relations
which have been actually determined for masses of varying sizes and at
different distances apart,--for snowflakes falling to the earth, for the