The distinctive capacity of human labor power is therefore not its ability to produce a surplus, but rather its intelligent and purposive character, which give it infinite adaptability and which produces the social and cultural conditions for enlarging its own productivity, so that its surplus product may be continuously enlarged.  From the point of view of the capitalist, this many-sided potentiality of humans in society is the basis upon which is built the enlargement of his capital.  He therefore takes up every means of increasing the output of the labor power he has purchased when he sets it to work as labor.  The means he employs may vary from the enforcement upon the worker of the longest possible working day in the early period of capitalism to the use of the most productive instruments of labor and the greatest intensity of labor, but they are always aimed at realizing from the potential inherent in labor power the greatest useful effect of labor, for it is this that will yield for him the greatest surplus and thus the greatest profit (38-39).