That's a radical policy. There are 72 million Turks, nearly all Muslim, who will end up with the right to move to the UK if Turkey is allowed to join. Turkey is not historically a part of the West, so it will mean establishing a precedent of Western countries dissolving themselves in a federation with non-Western ones.
Why would Cameron want to do this? Liberals like Cameron see society as being made up of millions of autonomous wills. But how can a society of competing wills be harmoniously regulated? The answer of right-liberals is that the hidden hand of the free market can regulate our self-directed purposes for the overall good of society.
So there is a focus on Economic Man and his activities in the free market - as this is what is thought to successfully harmonise individual "freedom" (i.e. autonomy).
What becomes authoritative, as a principle of social administration, are market outcomes. Countries are governed as if they were companies.
So back to the right-liberal Cameron. His first reason for wanting Turkey to join the EU? He thinks it will be good for the economy:
I ask myself this: which European country grew at 11% at the start of this year? Which European country will be the second fastest growing economy in the world by 2017? Which country in Europe has more young people than any of the 27 countries of the European Union? Which country in Europe is our number one manufacturer of televisions and second only to China in the world in construction and in contracting?...
That is the first reason I am here today and it is why I have chosen to come to TOBB, right in the heart of the Turkish business community.
And who does Cameron think opposes Turkish membership? Again, he sees things along economic lines. He imagines that the opposition comes from "protectionists" who fear free trade:
Every generation has to make the argument for free trade all over again and this generation will be no different. As we build our economic relationship there are some who fear the growth of a country like Turkey, who want to retreat and cut themselves off from the rest of the world. They just don’t get it...
So let me tell you what we are going to do to beat the protectionists. We are going to work harder than ever before to break down those barriers to trade that still exist, to cut the global red tape, like by streamlining customs bureaucracy and to work towards completing the trade round that could add $170 billion to the world economy...
We are welcoming new business to Britain. And we are delighted that so many Turkish people are visiting, studying, and doing business so successfully in the United Kingdom.
Today the value of our trade is over $9 billion a year. I want us to double this over the next five years. We cannot let the protectionists win the argument.
He is blind to the idea that the UK might exist for purposes other than trade. Questions of culture, of religion, of tradition, of distinct nations of people - all these are reduced to possible impediments to free trade that must not be allowed to interfere with running society along "rational" market lines.
And so we get to see the passionate side of Cameron, the Cameron who is angered by the idea that pesky issues of culture and civilisation might get in the way of economic objectives:
it makes me angry that your progress towards EU membership can be frustrated in the way that it has been...
I will remain your strongest possible advocate for EU membership and for greater influence at the top table of European diplomacy. This is something I feel very strongly and very passionately about. Together I want us to pave the road from Ankara to Brussels.
At least Cameron has shown decisively, early in his Prime Ministership, that he is a radical right-liberal rather than a genuine conservative. This must surely make it clear to the base of the Conservative Party that they must either rebel against the party leadership or else leave and build up another party or another political movement.
I don't want to always be presenting the views of those who betray. So I'll finish by linking to someone I don't know much about, except that he is a Conservative Party MEP who has written a good reply to Cameron: If Turkey joins the EU, we should leave. Roger Helmer is proof that it's possible to have a background in business and still put national sovereignty first.