value, _belief_, as well as desire and feeling, may often be a very significant phase in the value situation, and have a motivating power quite as great as the other phases. _Credit_, while it exists, is a real addition to the sum of values--has, that is to say, a real power in motivating economic activity, calling forth new productive efforts, and directing labor, capital, and enterprise to new channels. This is not, of course, asserting the doctrine of John Law. Credit cannot be manufactured out of whole cloth. Beliefs, at least to some extent, follow rational laws, and, except in moments of hysteria, there must be something for people to believe in before strong belief can emerge. Sometimes, of course, an unstable but momentarily powerful belief, based on nothing rational, may dominate a situation, and radically upset the existing scale of values--with a sad reaction following shortly after. And, in the absence of belief, the most rational justification for belief is impotent. Witness the bankruptcies, in times of panic, of men whose assets turn out later perfectly adequate, but who are unable to liquidate them at the time of the panic. Note, too, in this connection, the tendency in times of panic to turn to government for aid in sustaining values--to substitute for the waning social force of belief the power of a new legal force. A case parallel to the panic, as inducing a diminution of the total psychic energy of control, is presented by widespread epidemics. Gabriel Tarde, criticizing Mill's contention that all values cannot rise or fall, instances the general fall in all values which an epidemic occasions, and the recovery of values after the epidemic.[197] This criticism of Tarde's will not, of course, hold as against Mill's doctrine (indefensible on other grounds) which bases the relativity of values upon a logical definition, but it will hold as against the psychological doctrine of relativity under discussion. A further point is to be noted. Even granting that the sum total of social power of motivation is definitely limited, it still does not follow that the sum total of economic value is so limited. For not all of this social psychic energy goes into economic values. Religious, aesthetic, patriotic, moral values, all call for their share of this energy, and the amount given to each varies from time to time. This phase of the matter is discussed in detail by Professor Ross, in the chapter on "The Social Forces" in his _Foundations of Sociology_, and I shall not expand the discussion here.