We have free will. We make our own decisions. We have long taken these basic assumptions for granted. But what does neuroscience make of this? In this excerpt from the BBC Horizon special, "The Secret You," Marcus Du Sautoy (Oxford University) participates in a brain imaging experiment conducted by John-Dylan Haynes, a neuroscientist based in Berlin. And the results? Well, they force us to rethink things a bit. Goodbye Descartes. Goodbye mind before matter. Goodbye to consciousness and free will, as we traditionally like to think about them. And welcome to the world of neurons, to brain activity that makes your decisions before your conscious self is even aware of them. To delve deeper into all of this, you can watch Haynes give a 90 minute lecture here called "Unconscious determinants of free decisions in the human brain."