An action should have an actor (kartA). That means there should be someone to claim: “I am doing this”. Only humankind has this sense of agency, though all living beings naturally are active. Man is born as part of nature and lives as part of nature. But he does not realize his being an integral part of nature, and therefore is oblivious of the fact that his ability to know, ability of volition, and ability to do works are merely part of the creative function of nature. Because of this obliviousness he thinks he is the doer of all these actions. Such a man is called vimUDhAtmA (the stupefied one or the stupid). Only such stupid ones have the sense of agency and they alone have karma.