,612 THE ECONOMIC JOURNAL These words were written by Professor Marshall nearly twenty years ago; ? but their spirit still pervades his ?nost recent utterances. The want of the appropriate mathematical conceptions is not the only cause of the too common reluctance to accept the doctrine of the double nature of value. A difficulty also is presented by that which, according to Professor Marshall, is' the centre of the chief difficulty of every economic problem'.. the element of time. The forces of utility and disutility do not always act simultaneously, as in the simple case' where a person satisfies one of his wants by his own .direct action, as, for instance, when he picks blackberries,' up to the point when' the task of picking begins to cause weariness, which at last counterbalances the desire of eating, and equilibrium is reached.' Very generally the correspondence between value and efforts-and- sacrifices is the result of motives whose object is distant--such as the net advantages of an occupation for which a parent educates his son. Accordingly, the sect of economists who subordinate the principle of cost to that of utility are right so long as they confine attention to
single markets and short periods. The critics of Ricardo, and the
more damaging caricaturists who represent themselves as his followers, are mistaken if they expect that value should follow cost into .each particular transaction with the precision of a Labour-Exchange, such as haft-taught enthusiasts have imagined. Not only a 'long period,' but a stationary state would be required for the complete establishment of .equilibrium between cost and value. But the state of industry is never stationary, ' the economic conditions of the country are con- stantly changing, and the point of adjustment of normal demand to normal supply is constantly shifting its position. There are, indeed, constant tendencies towards that point as surely as, to use an old simile, there is a constant tendency of the surface of the sea towards a position of rest; but the moon and places, always therefore changing equilibrium of the sea is governed; less currents of the raging winds; the sun are always shifting their the conditions by which the and meanwhile there are cease- the surface is always tending towards a position of normal equilibrium, but never attains it.' We regret that the author has omitted this splendid passage from the second edition. He was perhaps deterred by the difficulty of con- veying through any physical analogy the distinction between the 'long' and ' short periods' in which the effects of economic forces may be worked out. We should have indeed to suppose the attraction of the 'moon and the sun,' in contrast to the terrene forces, to occupy a considerable time in being propagated to the surface of the sea ! The attraction of distant objects playing so large a part in the mechanics of industry, it concerns us to study the law of that attraction. The formula, precise as that of gravitation, is the inverse, or rather negative exponential. ' If h be the future amount of a pleasure of which the probability is p, and which will occur, if at all, at time t; and if /? ?- 1 + r, [where r is ' the rate of interest per ? In a review of Jevons's Theory in the ?lc?dem!l, April 1872.
