Exploitation is not a natural phenomenon nor is it moral category in and of itself (although its existence can- and perhaps should- provoke moral rejection and ethical reflection). Exploitation is a Marxist concept that tries to capture the essential mechanism of the capitalist system of production.
Labor exploitation by capital is produced because the social conditions that determine the capitalist mode of production make it possible for workers as a whole (salaried workers, according to the theoretical model analyzed by Marx in Capital) to work too much, not only producing a mere fraction of the social product that they themselves (and their families) consume in their lives- in this way allowing for the condition of “selling” their labor power and the reproduction of this condition- but also producing the product that replenishes the mode of production consumed by the work process and that is required by the ultimate beneficiaries of the system (the capitalists) for their own consumption and for the formation of new capital that allows for expanded reproduction. Profit is the monetary expression of surplus labor.
Therefore, exploitation doesn’t refer to salaries that are especially low nor work conditions that are especially hard (although the expression “savage exploitation” is appropriate to describe these situations). Exploitation refers to a state in which the workers, the producers, receive only a part of the value that they produce, independent from whether the salary is higher or lower or whether the work conditions are more or less hard.
Exploitation is also not about taking away from workers something that belongs to them, in which case this usurpation would be morally reprehensible. Marx insists that, in accordance with the “law of market exchange,” the seller of the commodity of labor power receives exactly the value of their commodity. Exploitation and the existence of non-paid work arise not from a violation of the capitalist laws of market exchange but rather their fulfillment. Exploitation is not an anomaly of the capitalist mode of production but rather one of its central characteristics. There is no such thing as a good, non-exploitative capitalism that is opposed to a savage, exploitative capitalism.
If we want to abolish exploitation, we shouldn’t think about reforming the relations of production within capitalism, rather, in terms of our aim, about the abolition of capitalism, which, of course, doesn’t involve any political or theoretical denial of the efforts of labor unions to change work conditions for the working class or of the fights that are being taken up in a good number of cities and countries around the world to improve their hard, sometimes very hard, situations.
References Guerrero, Diego. Un resumen completo de El Capital de Marx, Madrid, Maia Ediciones, 2008. Heinrich, Michael. Crítica de la economía política. Una introducción a El Capital de Marx, Madrid, Guillermo Escolar, 2918 (2ª edición). Traducción y estudio introductorio de César Ruiz Sanjuán. Marx, Karl. El Capital. Libro primero. Volumen I (OME 40), Barcelona, Grijalbo, 1975, capítulos VII y VIII, pp. 231-249 y 251-326 respectivamente. Traducción, presentación y notas de Manuel Sacristán.