To find the force due to a system of charges, we can find the force on a charge due to the other charges and add the vectors. In this context, my school text book says, "Superposition principle should not be regarded as obvious, or equated with the law of addition of vectors. It says two things: force on one charge due to another is unaffected by the presence of other charges, and there are no additional three-body, four-body,etc., forces which arise only when there are more than two charges". But since the force acting between two particels is given by Coulumbs law (which ignores the effect of other particles), isn't the superposition principle simply addition of vectors? And what does the last sentence about three-body and four-body forces mean? I think I am missing something in the definition of superposition principle.