Scientific talks can get a little dry, so I try to mix it up. I take out my giant hairy orangutan puppet, do some ventriloquism and quickly become entangled in an argument. I’ll be explaining my theory about how the brain — a biological machine — generates consciousness. Kevin, the orangutan, starts heckling me. ‘Yeah, well, I don’t have a brain. But I’m still conscious. What does that do to your theory?’

Kevin is the perfect introduction. Intellectually, nobody is fooled: we all know that there’s nothing inside. But everyone in the audience experiences an illusion of sentience emanating from his hairy head. The effect is automatic: being social animals, we project awareness onto the puppet. Indeed, part of the fun of ventriloquism isexperiencing the illusion while knowing, on an intellectual level, that it isn’t real.

Many thinkers have approached consciousness from a first-person vantage point, the kind of philosophical perspective according to which other people’s minds seem essentially unknowable. And yet, as Kevin shows, we spend a lot of mental energy attributing consciousness to other things. We can’t help it, and the fact that we can't help it ought to tell us something about what consciousness is and what it might be used for. If we evolved to recognise it in others – and to mistakenly attribute it to puppets, characters in stories, and cartoons on a screen — then, despite appearances, it really can’t be sealed up within the privacy of our own heads.

Lately, the problem of consciousness has begun to catch on in neuroscience. How does a brain generate consciousness? In the computer age, it is not hard to imagine how a computing machine might construct, store and spit out the information that ‘I am alive, I am a person, I have memories, the wind is cold, the grass is green,’ and so on. But how does a brain become aware of those propositions? The philosopher David Chalmers has claimed that the first question, how a brain computes information about itself and the surrounding world, is the ‘easy’ problem of consciousness. The second question, how a brain becomes aware of all that computed stuff, is the ‘hard’ problem.