I know Descartes was trying to help when he said "I think, therefore I am". But he didn't clear up the bigger question. I'm pretty sure I'm real - but how do I know the rest of you are?
I ask because I'm still anxious after four days of Jubilee coverage which unanimously presented a world which I am, by virtue of geography, a participating member of, yet did not recognise. I didn't have a problem with the visuals - I've seen Tower Bridge and Buckingham Palace with my own eyes, and accept them as concrete reality. But the undivided land basking in the hazy warmth of its Queen's glow, choked up with admiration for its monarch's selfless commitment to this greatest of great nations - where the hell's that?
I expect Royal correspondents like Nicholas Witchell to swoon with awe upon first sight of the Queen's hat, and column-chasing right-wing extremists like Kelvin McKenzie to tell me that the only people who don't swell with pride at the sight of the Royals on a boat are loony social outcasts. But when I hear serious journalists like Andrew Marr or Bonnie Greer stating that 86-year-old Elizabeth is looking "utterly gorgeous" and the entire UK is "filled with joy", I have to question the authority of my empirical knowledge. Especially regarding huge pockets of Northern Ireland and virtually all of Scotland.
The fascistic absolutism of the Jubilee media coverage is British anti-intellectualism at its worst. "The whole country is united by a patriotic pride," the BBC kept telling us. "Even the staunchest republican can't fail to be roused by the sight of Prince Phillip in a suit." Um ... in my experience, yes he can. We kept being instructed to celebrate the democratic freedoms our monarchy affords us but there was no sign of them in the BBC's reports. All dissenting voices had, it seemed, been kettled up for the weekend in a field outside the Watford Gap.
I have no axe to grind with the Windsors; I don't know much about them. But I find the notion, oft-expressed this week, that they embody the Greatness of Britain, rather suspect. There have been many mistakes and shames in this country's history, but what we have been good at is forward-thinking and creativity. Through argument, imagination and challenging the old, established systems, we have made seminal breakthroughs in science, technology, medicine and art.
Our greatest human exports, from Newton to Babbage, Shakespeare to The Stones, have been breakers of tradition - non-conformist, brave-hearted inventors, entrepreneurs and poets. So how can this totem of hereditary privilege, status and wealth, whose role is dependent on unquestioning acceptance of her fate and the relinquishing of personal opinion, embody the best of British?
There was the odd rumble, not of rebellion, but of suggestion that there might be bigger, more serious fish to fry, not least from the Archbishop of Canterbury. His thanksgiving sermon, in which he had a go at "ludicrous financial greed" of bankers and the "collective contempt for the unsuccessful and marginal" in modern society struck me as the one moment of sanity and righteousness in the entire festivities. No surprise then that the old academic was generally felt to have badly misjudged the mood.
So which is it? Either the Jubiltastic BBC version of the UK is a Kim-Jong-il inspired fantasy, or everything I've seen and heard my entire life is an illusion.
Descartes is no help. Maybe I'll give George Galloway a call instead.