The theory of value, then, is contained in the main postulates of the Marxian system rather than derived from them. Marx identifies this doctrine, in its elements, with the labor-value theory of Ricardo,[16] but the relationship between the two is that of a superficial coincidence in their main propositions rather than a substantial identity of theoretic contents. In Ricardo's theory the source and measure of value is sought in the effort and sacrifice undergone by the producer, consistently, on the whole, with the Benthamite-utilitarian position to which Ricardo somewhat loosely and uncritically adhered. The decisive fact about labor, that quality by virtue of which it is assumed to be the final term in the theory of production, is its irksomeness. Such is of course not the case in the labor-value theory of Marx, to whom the question of the irksomeness of labor is quite irrelevant, so far as regards the relation between labor and production. The substantial diversity or incompatibility of the two theories shows itself directly when each is employed by its creator in the further analysis of economic phenomena. Since with Ricardo the crucial point is the degree of irksomeness of labor, which serves as a measure both of the labor expended and the value produced, and since in Ricardo's utilitarian philosophy there is no more vital fact underlying this irksomeness, therefore no surplus-value theory follows from the main position. The productiveness of labor is not cumulative, in its own working; and the Ricardian economics goes on to seek the cumulative productiveness of industry in the functioning of the products of labor when employed in further production and in the irksomeness of the capitalist's abstinence. From which duly follows the general position of classical economics on the theory of production.

With Marx, on the other hand, the labor power expended in production being itself a product and having a substantial value corresponding to its own labor-cost, the value of the labor power expended and the value of the product created by its expenditure need not be the same. They are not the same, by supposition, as they would be in any hedonistic interpretation of the facts. Hence a discrepancy arises between the value of the labor power expended in production and the value of the product created, and this discrepancy is covered by the concept of surplus value. Under the capitalistic system, wages being the value (price) of the labor power consumed in industry, it follows that the surplus product of their labor cannot go to the laborers, but becomes the profits of capital and the source of its accumulation and increase. From the fact that wages are measured by the value of labor power rather than by the (greater) value of the product of labor, it follows also that the laborers are unable to buy the whole product of their labor, and so that the capitalists are unable to sell the whole product of industry continuously at its full value, whence arise difficulties of the gravest nature in the capitalistic system, in the way of overproduction and the like.

But the gravest outcome of this systematic discrepancy between the value of labor power and the value of its product is the accumulation of capital out of unpaid labor, and the effect of this accumulation on the laboring population. The law of accumulation, with its corollary, the doctrine of the industrial reserve army, is the final term and the objective point of Marx's theory of capitalist production, just as the theory of labor value is his point of departure.[17] While the theory of value and surplus value are Marx's explanation of the possibility of existence of the capitalistic system, the law of the accumulation of capital is his exposition of the causes which must lead to the collapse of that system and of the manner in which the collapse will come. And since Marx is, always and everywhere, a socialist agitator as well as a theoretical economist, it may be said without hesitation that the law of accumulation is the climax of his great work, from whatever point of view it is looked at, whether as an economic theorem or as a tenet of socialistic doctrine.

The law of capitalistic accumulation may be paraphrased as follows:[18] Wages being the (approximately exact) value of the labor power bought in the wage contract; the price of the product being the (similarly approximate) value of the goods produced; and since the value of the product exceeds that of the labor power by a given amount (surplus value), which by force of the wage contract passes into the possession of the capitalist and is by him in part laid by as savings and added to the capital already in hand, it follows (a) that, other things equal, the larger the surplus value, the more rapid the increase of capital; and, also (b), that the greater the increase of capital relatively to the labor force employed, the more productive the labor employed and the larger the surplus product available for accumulation. The process of accumulation, therefore, is evidently a cumulative one; and, also evidently, the increase added to capital is an unearned increment drawn from the unpaid surplus product of labor.

But with an appreciable increase of the aggregate capital a change takes place in its technological composition, whereby the "constant" capital (equipment and raw materials) increases disproportionately as compared with the "variable" capital (wages fund). "Labor-saving devices" are used to a greater extent than before, and labor is saved. A larger proportion of the expenses of production goes for the purchase of equipment and raw materials, and a smaller proportion—though perhaps an absolutely increased amount—goes for the purchase of labor power. Less labor is needed relatively to the aggregate capital employed as well as relatively to the quantity of goods produced. Hence some portion of the increasing labor supply will not be wanted, and an "industrial reserve army," a "surplus labor population," an army of unemployed, comes into existence. This reserve grows relatively larger as the accumulation of capital proceeds and as technological improvements consequently gain ground; so that there result two divergent cumulative changes in the situation,—antagonistic, but due to the same set of forces and, therefore, inseparable: capital increases, and the number of unemployed laborers (relatively) increases also.

This divergence between the amount of capital and output, on the one hand, and the amount received by laborers as wages, on the other hand, has an incidental consequence of some importance. The purchasing power of the laborers, represented by their wages, being the largest part of the demand for consumable goods, and being at the same time, in the nature of the case, progressively less adequate for the purchase of the product, represented by the price of the goods produced, it follows that the market is progressively more subject to glut from overproduction, and hence to commercial crises and depression. It has been argued, as if it were a direct inference from Marx's position, that this maladjustment between production and markets, due to the laborer not getting the full product of his labor, leads directly to the breakdown of the capitalistic system, and so by its own force will bring on the socialistic consummation. Such is not Marx's position, however, although crises and depression play an important part in the course of development that is to lead up to socialism. In Marx's theory, socialism is to come by way of a conscious class movement on the part of the propertyless laborers, who will act advisedly on their own interest and force the revolutionary movement for their own gain. But crises and depression will have a large share in bringing the laborers to a frame of mind suitable for such a move.

Given a growing aggregate capital, as indicated above, and a concomitant reserve of unemployed laborers growing at a still higher rate, as is involved in Marx's position, this body of unemployed labor can be, and will be, used by the capitalists to depress wages, in order to increase profits. Logically, it follows that, the farther and faster capital accumulates, the larger will be the reserve of unemployed, both absolutely and relatively to the work to be done, and the more severe will be the pressure acting to reduce wages and lower the standard of living, and the deeper will be the degradation and misery of the working class and the more precipitately will their condition decline to a still lower depth. Every period of depression, with its increased body of unemployed labor seeking work, will act to hasten and accentuate the depression of wages, until there is no warrant even for holding that wages will, on an average, be kept up to the subsistence minimum.[19] Marx, indeed, is explicit to the effect that such will be the case,—that wages will decline below the subsistence minimum; and he cites English conditions of child labor, misery, and degeneration to substantiate his views.[20] When this has gone far enough, when capitalist production comes near enough to occupying the whole field of industry and has depressed the condition of its laborers sufficiently to make them an effective majority of the community with nothing to lose, then, having taken advice together, they will move, by legal or extra-legal means, by absorbing the state or by subverting it, to establish the social revolution.

Socialism is to come through class antagonism due to the absence of all property interests from the laboring class, coupled with a generally prevalent misery so profound as to involve some degree of physical degeneration. This misery is to be brought about by the heightened productivity of labor due to an increased accumulation of capital and large improvements in the industrial arts; which in turn is caused by the fact that under a system of private enterprise with hired labor the laborer does not get the whole product of his labor; which, again, is only saying in other words that private ownership of capital goods enables the capitalist to appropriate and accumulate the surplus product of labor. As to what the régime is to be which the social revolution will bring in, Marx has nothing particular to say, beyond the general thesis that there will be no private ownership, at least not of the means of production.

Such are the outlines of the Marxian system of socialism. In all that has been said so far no recourse is had to the second and third volumes of Kapital. Nor is it necessary to resort to these two volumes for the general theory of socialism. They add nothing essential, although many of the details of the processes concerned in the working out of the capitalist scheme are treated with greater fullness, and the analysis is carried out with great consistency and with admirable results. For economic theory at large these further two volumes are important enough, but an inquiry into their contents in that connection is not called for here.

Nothing much need be said as to the tenability of this theory. In its essentials, or at least in its characteristic elements, it has for the most part been given up by latter-day socialist writers. The number of those who hold to it without essential deviation is growing gradually smaller. Such is necessarily the case, and for more than one reason. The facts are not bearing it out on certain critical points, such as the doctrine of increasing misery; and the Hegelian philosophical postulates, without which the Marxism of Marx is groundless, are for the most part forgotten by the dogmatists of to-day. Darwinism has largely supplanted Hegelianism in their habits of thought.