Abstract: Why don’t machines create value? The traditional interpretation is based on the distinction between “commodity duality” and “labor duality”. This explanation ignores an important theoretical node in the logic of Das Kapital: value is characterized by “paid”. Why is the contribution of natural forces "free" and that of human resources “paid”? The reason why value must be evaluated by the contribution of human resources and value must be determined by labor is that for workers, labor is “not free”, “involuntary”, “unconscious” activities, painful things, so it must be paid. Thus, it can be seen that “labor determines value” is the inevitable result of labor alienation.