Some 2,700 years ago in the ancient city of Sam’al, in what is now modern Turkey, an elderly servant of the king sits in a corner of his house and contemplates the nature of his soul. His name is Katumuwa. He stares at a basalt stele made for him, featuring his own graven portrait together with an inscription in ancient Aramaic. It instructs his family, when he dies, to celebrate ‘a feast at this chamber: a bull for Hadad harpatalli and a ram for Nik-arawas of the hunters and a ram for Shamash, and a ram for Hadad of the vineyards, and a ram for Kubaba, and a ram for my soul that is in this stele.’ Katumuwa believed that he had built a durable stone receptacle for his soul after death. This stele might be one of the earliest written records of dualism: the belief that our conscious mind is located in an immaterial soul or spirit, distinct from the matter of the body.
More than 2 millennia later, I was also contemplating the nature of the soul, as my son lay propped up on a hospital gurney. He was undertaking an electroencephalogram (EEG), a test that detects electrical activity in the brain, for a condition that fortunately turned out to be benign. As I watched the irregular wavy lines march across the screen, with spikes provoked by his perceptions of events such as the banging of a door, I wondered at the nature of the consciousness that generated those signals.
Just how do the atoms and molecules that make up the neurons in our brain – not so different to the bits of matter in Katumwa’s inert stele or the steel barriers on my son’s hospital bed – manage to generate human awareness and the power of thought? In answering that longstanding question, most neurobiologists today would point to the information-processing performed by brain neurons. For both Katumuwa and my son, this would begin as soon as light and sound reached their eyes and ears, stimulating their neurons to fire in response to different aspects of their environment. For Katumuwa, perhaps, this might have been the pinecone or comb that his likeness was holding on the stele; for my son, the beeps from the machine or the movement of the clock on the wall. [Continue reading…]