It may be that the 'surplus of each', as Condill puts it that which he has not utilized or does not expect to utilize immediately corresponds in quality and in quantity to the needs of the other: the whole surplus of the wheat owner is revealed, in the exchange situation, as being useful to the wine owner, and vice versa; in this case, what was useless becomes totally useful, through a creation of simultaneous and equal values on each side; what was estimated as null by the one becomes positive in the estimation of the other; and since the situation is symmetrical, the estimative values thus created are automatically equivalent; utility and price correspond exactly, with no residuum; the appraisal adjusting itself automatically to the estimate.