<P> Asimov's stories test his Three Laws in a wide variety of circumstances leading to proposals and rejection of modifications . Science fiction scholar James Gunn writes in 1982, "The Asimov robot stories as a whole may respond best to an analysis on this basis: the ambiguity in the Three Laws and the ways in which Asimov played twenty - nine variations upon a theme". While the original set of Laws provided inspirations for many stories, Asimov introduced modified versions from time to time . </P> <P> In "Little Lost Robot" several NS - 2, or "Nestor", robots are created with only part of the First Law . It reads: </P> <P> 1 . A robot may not harm a human being . </P> <P> This modification is motivated by a practical difficulty as robots have to work alongside human beings who are exposed to low doses of radiation . Because their positronic brains are highly sensitive to gamma rays the robots are rendered inoperable by doses reasonably safe for humans . The robots are being destroyed attempting to rescue the humans who are in no actual danger but "might forget to leave" the irradiated area within the exposure time limit . Removing the First Law's "inaction" clause solves this problem but creates the possibility of an even greater one: a robot could initiate an action that would harm a human (dropping a heavy weight and failing to catch it is the example given in the text), knowing that it was capable of preventing the harm and then decide not to do so . </P>

Where did the three cardinal principles originally come from