And the larger part of this argument is perfectly {193} true. In dealing with the activities of the few, we have taken those of the many for granted. This general assumption, however, though inevitable at the beginning of our inquiry, has been provisional only. To any scientific conception of what is done exclusively by the few, an equally scientific conception of what is done by the many is essential. We must measure the former by the latter, as we measure mountains by their respective heights above the sea-level. That such a discrimination between the work of these two bodies is possible may be doubted by some; and accordingly before we actually proceed to undertake it, we will dispose of the arguments that will be, and actually have been, advanced in proof of its impracticability, and set forth the principles on which it must be, and obviously can be, made. {195} BOOK III {197} CHAPTER I HOW TO DISCRIMINATE BETWEEN THE PARTS CONTRIBUTED TO A JOINT PRODUCT BY THE FEW AND BY THE MANY. In the first chapter of his _Principles of Political Economy_ Mill alludes to the question raised by certain thinkers, of “_whether nature gives more assistance to labour in one kind of industry than another_”; and he endeavours to show that the question is useless and unanswerable. In every industry, he says, there would be no product at all unless nature gave something and labour did something. Each is “_absolutely indispensable_” and the part played by each is consequently “_indefinite and incommensurable_.” “_When two conditions_,” he proceeds, “_are equally necessary for producing the effect at all, it is unmeaning to say that so much of it is produced by one, and so much by the other; it is like attempting to decide which half of a pair of scissors has most to do in the act of cutting, or which of the factors five and six contributes most to the production of thirty_.” If this argument is applicable to nature and labour as agents in the {198} production of commodities, it is equally applicable to the few and the many as agents in the production of social progress generally; and the crisp phrases and illustrations which Mill employs in formulating it, put in the clearest and most forcible manner possible the whole class of objections referred to at the close of the last Book.