How negative is British public opinion toward the European Union? It's pretty grim: according to the most recent Eurobarometer survey, from May 2011, more Brits believe that the European Union is bad for their country than those who think it's a good thing. In every other country in the union – even Greece! – poll respondents were more likely to call EU membership good for their country.

To give you a sense of just how deeply Euro-skeptical the U.K. has become, I've mapped out the Eurobarometer data, which you can see at the top of this page. For the data, I took the percentage of poll respondents who call EU membership "good for their country" and subtracted the percentage who say membership is bad. The U.K., again, is the only country with a negative outcome. Every other country seems to at least grudgingly accept that membership is worth the costs, with respondents in several countries endorsing it by a wide margin.

British  Prime Minister David Cameron could only hold off British distrust of the European Union for so long. In a speech today, Cameron promised that, within five years' time, he will hold a referendum on whether or not the U.K. should exit the EU.

Cameron's speech, like the rising Euro-skepticism that led to it, was as much about culture as it was about politics. He hit the traditional points about the U.K. having an independent identity and "the character of an island nation" – a line that's always made me picture Winston Churchill with a little umbrella in his Scotch. Though Cameron suggested that U.K. is better off within the union, he seems to know when he has to bow to public opinion. "We can no more change this British sensibility than we can drain the English Channel," he said.

It's interesting to compare the Eurobarometer data with a separate survey run by the Pew Global Attitudes project. Pew asked respondents in eight European countries whether they have a "favorable" or "unfavorable" view of the European Union. I subtracted the "unfavorable" responses from the "favorable" and mapped out the results, which are shown below:

You might notice that these numbers are much more likely to be negative than in the map up top. Respondents in the U.K., Czech Republic and Greece are all more likely to see the EU unfavorably than favorably. But what's striking is that Brits seem to be less pessimistic on this question.

In other words, there is a subset of British people who say that they have a favorable view of the European Union but that they do not want EU membership for their country. If that seems contradictory, maybe it is, but it also highlights the particular British view of Europe as something separate.

Churchill's famous quote, "We are with Europe but not of it," highlights the way that English nationalism and Euro-skepticism – even a sense that British islanders are not really European – reinforce one another. It's a way of thinking about Europe that has some parallels with, for example, the Greek ethnic nationalist movements that oppose EU membership. But ultimately, the idea that "we may be in Europe but are not truly European" is a uniquely British one.