Full Idea
Dworkin suggests that every plausible political theory has the same ultimate value, which is equality - in the more abstract and fundamental sense of treating people 'as equals'.
Gist of Idea
Treating people as equals is the one basic value of all plausible political theories
Source
report of Ronald Dworkin (Taking Rights Seriously [1977], 179-83) by Will Kymlicka - Contemporary Political Philosophy (1st edn)
Book Reference
Kymlicka,Will: 'Contemporary Political Philosophy (1st edn)' [OUP 1992], p.4
A Reaction
I associate this idea with Kant (who says they are equal by virtue of their rationality), so that's a pretty influential idea. I would associate the main challenge to this with Nietzsche.