Liberal Democrats' role in the Coalition Government offers the party a chance to re-define its foreign policy thinking, much as the Orange Book re-defined aspects of its economic thinking. The Orange Book is often seen as a rightward shift, so in what direction is Lib Dem foreign policy now moving?
The conflicts in Afghanistan and Libya have kept foreign affairs at the heart of UK politics, at a time when the Government is also conducting a major review of its defence spending - and this only a few years after opposition to the Iraq War became a defining issue (if not the defining issue) for many Liberal Democrats.
Deputy Prime Minister Nick Clegg sits (with fellow Lib Dems Chris Huhne and Danny Alexander) on the UK's year-old, American-inspired National Security Council, proving that foreign and security policy is very much a joint coalition concern - hardly a surprise, given that the Coalition Agreement itself includes a page on Foreign Affairs.
Clegg was with the Prime Minister and Foreign Secretary at the key foreign-policy meeting with President Obama when the latter was in London. David Cameron's comments (including on the possible need for a joint EU line on a possible Palestinian declaration of independence at the UN in September) at his joint press conference with Obama arguably reflect Clegg's publicly articulated thinking on a number of key issues.
Lib Dem ministers include Jeremy Browne at the Foreign Office and Nick Harvey at Defence, while Clegg himself made a major foreign policy speech as recently as March.
That speech, delivered in Mexico and entitled "An axis of openness: renewing multilateralism for the 21st century", offers many insights into where Clegg and his party might be going in foreign policy terms, offering as it does a qualified defence of "the principle of liberal interventionism...the principle that we have a collective responsibility to support freedom and protect human rights around the world".
In contrasting "law-abiding" liberal intervention in Libya with the "liberal vigilantism" of Iraq, Clegg seeks to move on from Iraq, "the lesson of (which) is not that intervention in support of liberal aims is always wrong". He is making a liberal intervention to rescue the very principle of liberal intervention from those Lib Dems who might attack it most.
In doing this, he is shifting the party back towards the thinking of Paddy Ashdown, the former Lib
Dem leader who wrote a whole book about liberal interventionism and who, it must never be forgotten, was a hawkish (and influential) advocate of British intervention in the wars in Bosnia and Kosovo.
The Lib Dems' opposition to the Iraq War temporarily overshadowed all other aspects of the party's foreign policy thinking, including its consistent support for the war in Afghanistan. Some Lib Dems' presence in the ranks of the "Not in my name!" stop the war brigade became a distorting prism, affecting both how the party viewed foreign affairs and how the party itself was viewed by itself and others.
Anyone who has spoken even briefly to Nick Clegg knows that he is a deeply nuanced thinker on questions of foreign policy. An emotion-led approach to such questions was never likely to satisfy him, however much it might occasionally have appealed to some of the party's hairier grassroots activists and even the occasional backbench Parliamentarian.
Clegg is able to build on a base of Lib Dem foreign-policy thinking that is surprisingly deep for a third party that was long in opposition. The academic and journalistic foreign-policy establishment includes more Lib Dems than one might expect, with many London-based diplomats privately conceding that the party punches above its weight on these matters.
Such foreign-policy experts are very much on the grown-up wing of the party, which is ever more in charge, especially now that the Lib Dems face the responsibilities of government. Many of the foreign-policy challenges which might have appeared easy in opposition are now, not surprisingly, turning out not to be so easy after all, hence the party's taking an increasingly measured, realistic approach to some very complicated problems.
If this adds to a growing tendency for the party to think maturely and dispassionately about foreign policy, then so much the better. Liberal Democrats are at their best when they apply cold reason and intellect to difficult issues, and foreign policy is no exception to that.
Nick Clegg's Mexico speech must be a call to arms for those who want Lib Dem foreign policy to be based on the liberal principles that the speech articulates. Just as the Orange Book drew together some of the best of the party's new thinkers on economics and public services, so it is now time for a similar exercise on foreign policy.