and
personal skill. Why is it, he would ask us, that valid reasoning has
proved to be so much more difficult in politics than in the physical
sciences?

Our first answer might be found in the character of the material with
which political reasoning has to deal. The universe which presents
itself to our reason is the same as that which presents itself to our
feelings and impulses--an unending stream of sensations and memories,
every one of which is different from every other, and before which,
unless we can select and recognise and simplify, we must stand helpless
and unable either to act or think. Man has therefore to create entities
that shall be the material of his reasoning, just as he creates entities
to be the objects of his emotions and the stimulus of his instinctive
inferences.

Exact reasoning requires exact comparison, and in the desert or the
forest there were few things which our ancestors could compare exactly.
The heavenly bodies seem, indeed, to have been the first objects of
consciously exact reasoning, because they were so distant that nothing
could be known of them except position and movement, and their position
and movement could be exactly compared from night to night.

In the same way the foundation of the terrestrial sciences came from two
discoveries, first, that it was possible to abstract single qualities,
such as position and movement, in all things however unlike, from the
other qualities of those things and to compare them exactly; and
secondly, that it was possible artificially to create actual
uniformities for the purpose of comparison, to make, that is to say, out
of unlike things, things so like that valid inferences could be drawn as
to their behaviour under like circumstances. Geometry, for instance,
came into the service of man when it was consciously realised that all
units of land and water were exactly alike in so far as they were
extended surfaces. Metallurgy, on the other hand, only became a science
when men could actually take two pieces of copper ore, unlike in shape
and appearance and chemical constitution, and extract from them two
pieces of copper so nearly alike that they would give the same results
when treated in the same way.

This second power over his material the student of politics can never
possess. He can never create an artificial uniformity in man. He cannot,
after twenty generations of education or breeding render even two human
beings sufficiently like eac