Here opens up, very evidently, a perfect labyrinth of complexity. But it was the labyrinth for which the earlier economist held, so he thought, the thread. No matter how dark the passage, he still clung tight to it. And his thread was his "fundamental equation of value" whereby each thing and everything is sold (or tends to be sold) under free competition for exactly its cost of production. There it was; as simple as A. B. C.; making the cost of everything proportional to the cost of everything else, and in itself natural and just; explaining and justifying the variations of wages and salaries on what seems a stern basis of fact. Here is your selling price as a starting point. Given that, you can see at once the reason for the wages paid and the full measure of the payment. To pay more is impossible. To pay less is to invite a competition that will force the payment of more. Or take, if you like, the wages as the starting point: there you are again,--simplicity itself: the selling price will exactly and nicely correspond to cost. True, a part of the cost concerned will be represented not by wages, but by cost of materials; but these, on analysis, dissolve into past wages. Hence the whole process and its explanation revolves around this simple fundamental equation that selling value equals the cost of production. This was the central part of the economic structure. It was the keystone of the arch. If it holds, all holds. Knock it out and the whole edifice falls into fragments. A technical student of the schools would digress here, to the great confusion of the reader, into a discussion of the controversy in the economic cloister between the rival schools of economists as to whether cost governs value or value governs cost. The point needs no discussion here, but just such fleeting passing mention as may indicate that the writer is well and wearily conversant with it.