Finally, the human capacity to perform work, which Marx called “labor power,” must not be confused with the power of any nonhuman agency, whether natural or man made. Human labor, whether directly exercised or stored in such products as tools, machinery, or domesticated animals, represents the sole resource of humanity in confronting nature. Thus for humans in society, labor power is a special category, separate and inexchangeable with any other, simply because it is human. Only one who is the master of the labor of others will confuse labor power with any other agency for performing a task, because to him, steam, horse, water, or human muscle which turns his mill are viewed as equivalents, as “factors of production.” For individuals who allocate their own labor (or a community which does the same), the difference between using labor power as against any other power is a difference upon which the entire “economy” turns. And from the point of view of the species as a whole, this difference is also crucial, since every individual is the proprietor of a portion of the total labor power of the community, the society, and the species.