[1609]. The number of a class is the class of all classes similar to the given class.—Russell, Bertrand.

Principles of Mathematics (Cambridge, 1903), p. 115.

[1610]. Number is that property of a group of distinct things which remains unchanged during any change to which the group may be subjected which does not destroy the distinctness of the individual things.—Fine, H. B.

Number-system of Algebra (Boston and New York, 1890), p. 3.

[1611]. The science of arithmetic may be called the science of exact limitation of matter and things in space, force, and time.—Parker, F. W.

Talks on Pedagogics (New York, 1894), p. 64.

[1612].

Arithmetic is the science of the Evaluation of Functions,

Algebra is the science of the Transformation of Functions.

—Howison, G. H.