|The law of returns can be established by what mathematicians call an indirect proofthat is, by assuming the law to be false, and then showing how that assumption leads to a contradiction or absurdity. Suppose that, contrary to the law, the average return either remains constant or else increases indefinitely after f increases past a certain point f0. Past this point, therefore, repeated increments f in factor F, with no additional input of the other factors, will continue to produce increments c in the production of consumer good C such that c/f is greater than or equal to the average return at f0. Such continuing production from increases in F alone, however, implies that good C is generated by just one scarce factora circumstance shown to be impossible at the beginning of this discussion (p. 4.4:42). Q. E. D.