Number is limited multitude or a combination of units or a flow of quantity made up of units; and the first division of number is even and odd. - Nicomachus

Scientific number, being set over such things as these, should be harmoniously constituted, in accordance with itself; not by any other but by itself.

Since of quantity, one kind is viewed by itself, having no relation to anything else, as 'even,' 'odd,' 'perfect,' and the like, and the other is relative to something else, and is conceived of together with its relationship to another thing, like' double,' , greater,' 'smaller,' 'half,' 'one and one-half times,' 'one and one-third times,' and so forth, it is clear that two scientific methods will lay hold of and deal with the whole investigation of quantity: arithmetic, [with] absolute quantity; and music, [with] relative quantity.

Bodily, material things are... continuously involved in continuous flow and change—in imitation of the nature and peculiar quality of that eternal matter and substance which has been from the beginning... The bodiless things, however, of which we conceive in connection with or together with matter, such as qualities, quantities, configurations, largeness, smallness, equality, relations, actualities, dispositions, places, times, all those things... whereby the qualities in each body are comprehended—all these are of themselves immovable and unchangeable, but accidentally they share in and partake of the affections of the body to which they belong. Now it is with such things that 'wisdom' is particularly concerned, but accidentally also with... bodies.