Toward the end of high school Ernst and I went to an Italian café near the Leidseplein. Enjoying a cappuccino--for us a recent discovery--we discussed an issue of the Scientific American devoted to the living cell. More and more was becoming known about this smallest unit of life. How it divides itself and how hereditary information was coded chemically. The expectation was that eventually all life processes would be understood, including those in the human brain and consciousness.
``But'', I objected, ``look at our school-book of biology. It describes the process of hearing. `Sound consists of airwaves. These arrive at the tympanum of the ear, where they are transformed into mechanical movements and then into pulsating nerves. The signal of these nerves arrives at the cortex of the brain and then we hear.' This explanation is utterly unsatisfactory.'' What exactly does happen at the cortex? This was not yet known. But that was not our main problem. It seemed that no matter what science will find out about brain processes, there will always be a gap between the theory and our personal experience.
``Actually,'' I continued ``there is already a puzzle about the fact that we seem to have our own consciousness. Why is it that you are you and I am I? Why am I not you? From the data we have, we only can say that this place here is a café and in this corner there are two persons discussing. In order to state the asymmetry between us, one could say that one of the two does not have eyes5. Indeed I can see only your eyes, not mine. But I cannot say that that person is me. The only thing I can say is that one of the persons is having no eyes and that that person is the one talking right now!''
Some years later I met Michael Corner, a colleague of my father. He was a brain specialist, and I asked him what he thought about the consciousness problem. The answer was remarkable: ``In our field we do not speak about consciousness. It is banned from our scientific language. But in my free time I do think about it often6.''
After leaving school Ernst and I continued different careers. He started to study biology, did his bachelors, but then stopped, as he did not want to kill animals. Perhaps he would have liked the study of etiology. Instead Ernst became an extremely virtuous pop musician. His groups7 enjoyed a lot of success in the Netherlands; for his second group the high popularity in the 1980ies (and as a come back in 2000) had neither been equaled before nor after. I started to study mathematics. I did finish a masters, but became more interested in the process of doing mathematics than in the subject itself. My PhD8 was in the field of mathematical logic. This subject answers questions like why there are axioms and what is their role in mathematics. It moreover distinguishes provability from truth. All very fascinating, but I would give all my established results in this field for knowing the answer to the hard consciousness problem.