Asking how you tell what's real and what isn't sounds like an obvious question. But in this series of six programmes, James Burke shows that the more you think about it the harder it is to answer. After all, what have you got-apart from your five senses - to prove those senses are giving you the real thing? When it comes to deciding what is out there, your brain acts like a private detective. Your senses pick up clues and the brain solves the mystery. Trouble is, it's easier than you think to fool the best private eye in the world.

Inside your brain is a complex map of your world. But sometimes you don't let it tell you everything it knows. And sometimes you believe the evidence of your own eyes, when you should be letting your ears do the talking. So how do you know what's real and what isn't? The answer is not as simple as you might think. Tonight, in the second of a series of six programmes, James Burke goes to the circus, climbs Blackpool Tower, and turns upside down in order, to discover how you know where you are, and which way is down.

The clock in your head that tells you when reality exists, it only does so for you - not anybody else. And it runs fast or slow depending on your mood. So - what time is it? And why is this writing in your past? In the third of a series of six programmes, James Burke spends 30 of his minutes (not necessarily yours) looking at why the world around you can't exist ' now ' for everybody. This programme will be short, or long, depending on you. Its real length? Who knows?

What was it that gave you the confidence to pick up a copy of RADIO TIMES? Was it because all the previous times you'd done it, nothing had gone wrong? In the fourth search for reality James Burke looks at why your memory is you and everything around you. And if you're forgetful - does that alter you? Or reality? Will you remember to watch at 8.30?

If you have a moment - think about your brain. OK? Now - if you usually think with your brain, what did you just use to think with, when you thought about your brain? This week, in the search for reality James Burke looks inside your head to see where the ' I ' is and ends up at a party. You may enjoy it - wherever ' You ' is

The fact that you know what these words mean may be the reason why the entire Universe exists for you. The shape of reality may be fixed by the way you use grammar rules you learned at school! You have the power to wipe out anything with a negative. In the last of these journeys into your mind, James Burke investigates the extraordinary ability everybody has to make what they mean.