For the specific magnitudes here at issue, therefore, the categories of variables magnitudes, of functions and the like, are merely formal, as we said earlier, because they are still too general to contain the kind of specificity to which the whole interest of differential calculus is directed, nor can this specificity be developed out of it analytically; they are as such simple, insignificant, easy determinations that are rendered difficult by importing into them that which is not in them, in order then to derive it from them, namely the specific determination of differential calculus.