The term "liberal" is the most overly flexible idea of contemporary political discourse. According to that comically overblown purveyor of rightwing agitprop, Ann Coulter, liberals are defined by their support for big government, abortion and homosexuality and their hostility towards gun control, patriotism, and God.

The titles of her books tell the story of a woman obsessed: Slander: Liberal lies about the American Right (2002), Treason: Liberal Treachery from the Cold War to the War on Terrorism (2003), How to talk to a Liberal (If You Must) (2004), Godless: The Church of Liberalism (2006), Guilty, Liberal Victims and their Assault on America (2009) and her latest offering, Demonic: How the Liberal Mob is Endangering America (2011). These books have sold in their hundreds of thousands, reflecting a popular expression of angry US conservatism.

But it would confuse a great many of Coulter's whooping audience to discover that the only other political philosophy that can match her vitriolic hostility to liberalism is that of communism. Here, for example, is Mao Zedong writing in 1937:

"Liberalism is extremely harmful in a revolutionary collective. It is a corrosive, which eats away unity, undermines cohesion, causes apathy and creates dissension. It is an extremely bad tendency. Liberalism stems from petty-bourgeois selfishness, it places personal interests first and the interests of the revolution second."

Similar sentiments can be found in Karl Marx's writings. The Coulter-type association of liberalism and the left is clearly more than a little problematic.

Indeed, it is arguably more persuasive to see liberalism as a philosophy of the right. Few books defined the Thatcher-Reagan era more than Robert Nozick's Anarchy, State and Utopia (1974) in which it is argued that taxation is fundamentally a form of slavery – the state forcing taxpayers to give up a proportion of their income, which is effectively the state forcing taxpayers to work for the state without pay ie slavery. This argument for a minimal state, and specifically its hostility to the welfare state, is Coulter-like in its worldview, but originates in an uncompromising commitment to human freedom. And it is this commitment to freedom that has traditionally been understood as the defining quality of liberalism.

There is, then, much confusion about the very idea of liberalism. According to that other rightwing cheerleader of modern capitalism and passionate proponent of liberalism, Friedrich Hayek, this confusion originates in the fact that liberalism has two basic tributaries. Beginning in England in the 17th century, "Whiggish" liberalism places its emphasis on individual freedom and the rule of law, whereas the later continental liberalism was a movement of the French Enlightenment representing "a demand for an emancipation from all prejudice and all beliefs which could not be rationally justified, and for an escape from the authority of 'priests and kings'". But even Hayek's picture is considerably oversimplified. For, as the historian Quentin Skinner has rightly pointed out, there is a long tradition of political thought concerning human freedom, going back at least to the Romans, that considerably pre-dates early modern liberalism.

I offer this short excursus on the complex topography of liberalism as a way of setting the stage for the reflections that follow in the next several weeks. As much as anything, I will be seeking to explore my own shifting instincts about liberalism in conversation with contributors. For me this is a more speculative project than those undertaken before, as I remain to some degree conflicted about a number of the issues that liberalism raises. And as a way of focusing these reflections, I have chosen to use the work of Isaiah Berlin as a framework. It seems to me that Berlin typifies a certain sort of 20th-century liberalism and that, through him – and not least through his famous distinction between positive and negative liberty – we may critically approach some of the weighty themes of human freedom.