One of the marked features of economic thought has been a decline in the older dogmatism, a quickening of scepticism and a reawakening of controversy. The effect of the friction on price will be a double one-one direct in permitting spatial differences to occur, one indirect in changing the equilibrium-level itself. The classical theory of competition would appear to founder on this basic contradiction : that when competition is concretely defined as operating amid the sort of frictions which the real world must necessarily contain, the "competitive equilibria" cannot define the situation even as approximations. Some element of retarding friction seems necessary to the operation of competition at all. The crucial distinction is rather between the type of law which one can postulate of a world of perfect certainty and that which operates where various types of uncertainty prevail.