One of the first and most difficult steps in a science is to conceive clearly the nature of the **magnitudes** about which we are arguing.

— Chapter III, Theory of Utility, p. 78

The relationship of point to line bothered the Greeks and led Aristotle to separate the two. Though he admits points are on lines, he says that a line is not made up of points and that the continuous cannot be made up of the discrete. This distinction contributed also to the presumed need for separating number from geometry, since to the Greeks numbers were discrete and geometry dealt with continuous **magnitudes**.

— Morris Kline,

Those skilled in mathematical analysis know that its object is not simply to calculate numbers, but that it is also employed to find the relations between **magnitudes** which cannot be expressed in numbers and between functions whose law is not capable of algebraic expression.

— Antoine Augustin Cournot.

[P]hysical quantities ... suffice to determine the rate of profit (and the associated prices of production) […] [I]t follows that value **magnitudes** are, at best, redundant in the determination of the rate of profit (and prices of production). […] Marx’s value reasoning––hardly a peripheral aspect of his work––must therefore be abandoned, in the interest of developing a coherent materialist theory of capitalism.

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