When conducting an interview with someone who has just written a book or a play, or embarked on a new venture, the natural starting point is ask where the idea came from.
However, in the case of American author and neuroscientist David Eagleman I know in advance what his answer will be - that he does not have a clue.
This is not to say that he has failed to think seriously on the subject - actually, for the past year or two he has been thinking about little else. Eagleman's new book, Incognito: The Secret Lives of the Brain, covers this area pretty extensively. In fact, he reveals, he was originally going to call it "Where Ideas Come From".
So, I say, as we sit down for a coffee at his London hotel, where did the idea for the book come from? Eagleman, youthful looking and casual in jeans and T-shirt cannot give me a simple answer. "The thing I emphasise in the first chapter is that ideas are underpinned by physical stuff. Essentially, your entire life - a sum of your genetic inheritance and your experiences which are all bubbling away inside you - is what gives you the idea. You can't have an idea which isn't a synthesis of everything which has happened before. Everything we recognise is only in relation to everything we've recognised before. So where did the idea for the book come from? I have absolutely no idea."
Eagleman has written scientific studies on subjects as varied as synesthesia and the internet. He is also a best-selling fiction writer - his novel, Sum: Forty Tales from the Afterlives, has been translated into 22 languages.
However, if Eagleman's own thesis is correct, he can take very little credit for Sum's success. According to him, while we may think we are in control of our body and our minds, in fact our conscious thoughts and actions make up only a tiny proportion of our being. For the most part we are running completely on auto-pilot - parts of our brain that we have no access to are ensuring that our bodies run smoothly, and our subconscious minds heavily influence the decisions which we think we are making.
Eagleman says: "Language is an interesting example. When you speak you are really on auto-pilot. Words come out of your mouth much faster than your conscious brain can keep up with. That's not to mention the detailed movements of your mouth, lips and tongue which enable you to make the appropriate sounds at great speed. If you started to analyse exactly what you were saying and how you were saying it, you wouldn't be able to speak at all."
He adds: "While we have been sitting here, at various times we have both shifted position. These are sophisticated movements based on blood flow and when things are getting pinched off. We don't know any of that stuff, we just do it."
You may also not be in control of the decisions you were fairly sure you made deliberately and knowingly – like, for example, your choice of partner. "There are various levels of decision which might go into your choice of a girlfriend," says Eagleman. "There is a chemical level. A woman might seem beautiful to you, but she would not seem beautiful to a frog - beauty is not objective, it is functional. But it's not just chemical stuff. You are also asking yourself questions, like what your mother would think of this person, how she would fit into your circle of friends, how do you feel about her tattoos. Then there are the subconscious things, like her name. People are much more likely statistically to choose a partner whose name begins with the same letter as their own. We also choose our jobs that way. I gave a talk yesterday morning on this subject and one guy raised his hand and said: 'I'm Robert the researcher", another one said: 'I'm Paul the pollster".
Some people might find it scary to think that they are not really in control of either their bodies or their minds most of the time, but Eagleman is not among them. He feels there are huge pluses in finding out that our conscious thoughts and actions are not as conscious as we think them to be. "When Galileo discovered that we were not, as was previously thought, at the centre of the universe, people called that 'the dethronement of man'. But I think dethronements have upsides. If you look at the universe, it turns out it is far more wondrous and awe-inspiring than we ever imagined. The same happens with the brain. Ok, we're not the ones driving the boat but it turns out we're more wondrous and subtle than we ever imagined. I think it's going to enhance our view of ourselves."
Modern neurology is pointing us in different directions. To use a political analogy, while the brain was once thought of as a kind of dictatorship, it is now viewed as a group of competing factions - the "neural parliament" as Eagleman calls it.
He uses this to explain the hitherto inexplicable behaviour of Hollywood actor and director Mel Gibson who, on famous day in July 2006, had lunch with Jewish friend Dean Devlin in Los Angeles and a few hours later launched in to an antisemitic tirade at a policeman in Malibu when he was stopped on suspicion of drunk-driving.
Eagleman thinks he has an explanation for Gibson's behaviour. "There is not a single you. You are made up of these competing sub-populations, so there might be parts of his brain which are antisemitic and parts of his brain which aren't. At the more banal end of the spectrum I might offer you a chocolate chip cookie. Part of you wants it, part of you doesn't, so which is the real you? The answer is both.
"In his written apology Gibson made a mistake - he said he shouldn't have thought those things. We all have inappropriate thoughts from time to time. The thing he did wrong was saying those things. I'm not making excuses for Gibson. I'm Jewish and I was displeased by his comments but I don't think you should put him in a box and say he is or is not an antisemite. The truth is he's both."
Although neuroscience is changing the way we think of the brain, and our own consciousness, Eagleman believes we are just scratching the surface of what goes on inside our own heads.
"There's a saying that if the brain was simple enough to be understood, then we wouldn't be sophisticated enough to understand it," he says.