A friend was telling me about a dream she'd had, which featured an acquaintance of ours, an American battleship and two tyrannosaurs duelling with steak knives. (To reveal any more details would be ungentlemanly, and also scupper a surprisingly profitable blackmail scheme.) What could it mean? she begged.

With an impressive and sexy lack of hesitation, I replied that it meant nothing at all. No one buys all that drivel about sifting dreams for messages from the id, I scoffed. There's no code where flying equals sex and Anne Robinson equals death. No no no. Dreams are simply a jumble of thoughts, a sort of psychic feedback, a cloud of cerebral dust. I'd come up with a total of 26 such metaphors before it occurred to me that I didn't know anything about the subject whatsoever.

I mean, what are dreams? How do they work? Why do they feature beetroot and Julia Sawalha so often? And would it make any difference to our lives if they didn't exist, apart from depriving schoolchildren of a useful formula for rounding off stories?

It was very upsetting. One minute I'd been enjoying my favourite type of conversation - I do lots of talking, someone else does lots of nodding - the next I'd stumbled across something new to add to my Embarrassing Ignorance List, which was already quite long enough. The EIL comprises facts so obvious it is hard to admit, even to yourself, that you don't know them. How do they get toothpaste to come out in neat, red and white stripes? Why do boomerangs come back? How do computers work? And for that matter, batteries? And, you know gravity? I know what it does, but what, essentially, is it?

This anxiety hit me after only a couple of years in the working world. At school and in further education you can always imagine that someone has your learning in hand, and is about to explain just what Watergate was all about. Afterwards, you start to panic. Who's going to tell me who Marco Polo was now? How long can I continue to let conversations drift past, thinking to myself, "Ah well, I'll understand it when I'm older?"

If I had to blame external forces for this - and, frankly, I'd prefer to - I'd say it was down to my doing an arts course at university, and being encouraged to think it was the height of banausic stupidity to remember anything more useful than the definition of "sprung rhythm". (And no, I don't know the definition of sprung rhythm or banausic.) Or perhaps it's because I'm a few years too old to have had computer science classes at school, and a few years too young to benefit from the hilariously archaic idea that history classes teach you names and dates.

I'm certain it's a generational phenomenon. In my teens, my Dad had no trouble helping me with the Integration and Differentiation questions in my maths homework. He remembered them from school and he was a fortysomething at the time. Whereas I forgot what Integration and Differentiation were days after the exam.

So, this trauma will bounce back at me if I have children. They'll say: "Daddy, when were the Crusades?" And I'll say: "Oh really, don't be so banausic, Julia. Go and read an improving magazine." And when they've gone to sleep, I'll sneak into their bedrooms, borrow their textbooks, and educate myself again, from scratch.