In every income which has anything to do with other incomes, it is necessary to distinguish its immediately productive side, and its profit or acquisition side. It is necessary, in the first place, that all the products made by private parties should, so to speak, be put into the common treasury of the national economy, and that each should thence draw his own private revenue. Justice requires that there should be a perfect correlation between the two; that each should enjoy precisely the quota of the national income to the production of which his person or his property contributed. A just appreciation of the relative productive power of the divers branches of labor constitutes one of the chief bulwarks against the inroads of destructive socialistic theories. The person who calls a good doctor or a good judge unproductive should, to be consistent, call those who by their greater intelligence are fitted to superintend agricultural and industrial enterprises unproductive, also, as is done by the coarser socialists with their apotheosis of mere manual labor. Unfortunately, such a settlement as is above contemplated among the different factors of production, whose owners are desirous to divide the common product among them, is possible only where the factors of production are either of the same kind, or can be reduced to a common denominator.[148-1] But if justice pure and simple were meted out, no man could subsist. Love or charity must supplement justice in order to assist those (and especially such as without any fault of theirs) who are not able to produce anything, or enough to supply those wants, for instance, children and the poor.