Taking a class of things collectively is contrasted with taking them separately or distributively. Not knowing which is meant can be fatal. Article II of the American Bill of Rights states that ‘a well-regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed’, and is unfortunately ambiguous over whether what is being created is the right of the citizens collectively to keep and bear arms (i.e. to organize themselves militarily, or to sustain a militia), or the right of each individual separately, and not well regulated, to amass his or her own arsenal. In other parts of political philosophy the distinction surfaces when we know what each person prefers individually, but are unable to construct a unique social welfare function telling us what ‘they’ prefer as a whole or collectively. See also Arrow’s theorem, general will, prisoners’ dilemma.