As Eagleton explains, Milton was a key figure in the English Revolution which saw the temporary establishment of an English Republic in the 1650s. He defended the rights of free speech and popular sovereignty (though he was by no means a democrat in any straightforward sense). As Quentin Skinner has argued in depth, Milton belonged to a generation of 'neo-roman' thinkers of this time who saw the central evil in politics as arbitrary power. To be unfree is not simply to suffer interference from another; it is to live under the shadow of potential interference which lies at someone else's discretion. Jean-Jacques Rousseau was echoing Milton's thinking when he wrote that 'the worst thing that can happen in human affairs is to find oneself living at the mercy of another.'
Milton's conception of freedom as 'non-domination' (to use the term coined by Philip Pettit) retains all its force and relevance for us today. Not least, it continues to provide a vital standard against which to judge the British executive and its impatience with inconveniences such as the Human Rights Act which act as a break on its arbitrary power.
In addition, as later republicans saw, it offers an important basis for evaluating our economic and social institutions. How far does capitalism render individuals vulnerable to domination in the workplace, for example? What kind of institutions do we need to prevent domination in the workplace and in the home?
Also important is Milton's conception of politics and civic life. As David Marquand reminds us in his recent book Britain Since 1918, Milton belongs to that dissident tradition of 'democratic republicanism' in British politics which insists on seeing politics as a matter of active participation and 'sinewy discoursing': not the counting of heads, or the passive reflection back to people of their preferences, but common deliberation and mutual learning animated by a commitment to find a common good.
So let's raise a glass - if you're a Puritan tee-totaler, it can of course be a glass of orange juice - to John Milton and to the unfinished, but ongoing project of republican transformation.