We are still concerned with _things_ which exist in space and move about in space; and even if these things are small and are not very familiarly known, no intellectual revolution is demanded to enable a man to understand the words of the scientist who is talking about them, and to understand as well the sort of reasonings upon which the doctrine is based.
9.

MATHEMATICS .-- Let us now turn to take a glance at the mathematical sciences.

Of course, these have to do with things sooner or later, for our mathematical reasonings would be absolutely useless to us if they could not be applied to the world of things; but in mathematical reasonings we abstract from things for the time being, confident that we can come back to them when we want to do so, and can make use of the results obtained in our operations.
Now, every civilized man who is not mentally deficient can perform the fundamental operations of arithmetic.

He can add and subtract, multiply and divide.

In other words, he can use _numbers_.