Bernard Williams, answered from the texts and cited to the page.
Politics has its own sources of legitimacy distinct from prior moral theory. The dominant tradition of liberal political philosophy (Rawls's original position, Habermas's discourse ethics) is moralism: the imposition of pre-political moral standards on what should be a distinctively political form of legitimation.12 Political realism, the alternative, takes politics seriously as its own domain.
The Basic Legitimation Demand (BLD) is the requirement that any state offer a justification of its power that the subjects can accept — not a pre-political moral justification, but a justification that makes sense within the historical, cultural, and political situation in which the state and the subjects find themselves.34 The BLD is internal to politics in the sense that it does not require deriving political legitimacy from a moral theory independently established; it is also genuinely demanding — a state that cannot offer such a justification (a tyranny, a colonial occupation, an arrangement that systematically excludes some subjects from the conditions of legitimation) is illegitimate by the BLD's own internal standard.
The anti-moralism is not anti-moral. It is the recognition that political legitimacy is not a derivative form of moral acceptability and that the political question — what should we do, here, now, given the historical situation we are in — is not answerable by appeal to a moral theory developed elsewhere.5
It will be familiar how, in various ways, PM can seek to ground liberalism. I shall try to contrast with PM an approach which gives a greater autonomy to distinctively political thought. This can be called, in relation to a certain tradition, "political realism." Associated with this will be a quite different approach to liberalism.In the Beginning Was the Deed, pp. 3–4
But we get beyond this to any distinctively liberal interpretation only given further assumptions about what counts as legitimation. It will be seen that these further conditions contain rejections of some things that certainly have been accepted as legitimations in the past. Moreover, they refer to demands for legitimations where no such demands were made in the past.In the Beginning Was the Deed, p. 8
It has to be something in the mode of justifying explanation or legitimation: hence the BLD. The answer is all right as far as it goes, but more needs to be said about how a demand for justification arises, and how it may be met. One thing can be taken as an axiom, that might does not imply right, that power itself does not justify.In the Beginning Was the Deed, p. 6
So we have: (a) Mere incompetence to protect a radically disadvantaged group is an objection to the state. (b) The mere circumstance of some subjects' being de facto in the power of others is no legitimation of their being radically disadvantaged. This implies that slavery is imperfectly legitimated relative to a claim of authority over the slaves: it is a form of internalized warfare, as in the case of the Helots.In the Beginning Was the Deed, p. 5
They recognize, for instance, rights of free speech; in the first instance, because it is important that citizens and others should know whether the BLD is being met. Liberals will also add at least the following: (a) Rationalizations of disadvantage in terms of race and gender are invalid.In the Beginning Was the Deed, pp. 7–8
In the Beginning Was the Deed (2005, posthumous) and Geuss's Philosophy and Real Politics (2008) inaugurated the contemporary political-realism revival in Anglophone political philosophy. The major liberal-political-theory targets are Rawls's original position and Habermas's discourse ethics, both of which Williams treats as moralism in the sense defined. Geuss is the major fellow-traveller; the realism tradition has since been developed by Matt Sleat, Edward Hall, and others. Krause's chapter in Callcut on "Political Agency and the Actual" engages the realist position substantively; Kutz's "Against Political Luck" pushes back. The position remains contested; mainstream Anglophone political philosophy is still largely Rawlsian.