- A robot may not injure a human being or, through inaction, allow a human being to come to harm.
- A robot must obey the orders given it by human beings except where such orders would conflict with the First Law.
- A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws.
In "The Evitable Conflict" the machines generalize the First Law to mean:
- No machine may harm humanity; or, through inaction, allow humanity to come to harm.
This was refined in the end of Foundation and Earth, a zeroth law was introduced, with the original three suitably rewritten as subordinate to it:
- A robot may not injure humanity, or, by inaction, allow humanity to come to harm.
