Who am I? Ask your bacteria.
The question “Who am I?” has been a mainstay of philosophy for centuries, at least, if we discount “me” as a complete response. It might even be the mother of philosophy, as “who am I?” was probably asked before the more difficult, “why am I?”. Of course, “what do you want to do now?” was probably asked even earlier, but that only led to the birth of the shopping mall.
Thomas Aquinas gave us an answer (cribbed from Aristotle, and then filtered through a theological perspective). He said that we are defined by our body plus our intellect, a soul, and together these two describe who each of us is. These two aspects of ourselves are not distinct entities; the soul, he said, was the form, or principal, that allows our bodies to live. Our soul, he further defined, had an intellectual aspect that was unique to humans. It also has a sentient activity, that is, it could sense and perceive our environment. This part of our soul is shared with animals, and arises from the activity of the body and soul acting as one. The intellectual aspect is unique to humans, he thought. Together, all these defined who we were. Separate they have little meaning.
Attributing our thinking processes to regions of the brain based on a comparison to the brain of more simple animals is in part due to Thomas Aquinas. And the fact that some people really do have a ‘reptile brain’ (they’re called lawyers).
This description of what a human being is has stayed with us, and is still largely in line with Catholic church doctrine. It is in many ways a largely materialist perspective; the soul is dependent on the body, and if the body goes, so does anything that we would think of as being “ourselves”. Divine intervention, he believe, could preserve our sense of self, but the naturalistic aspects of his description matches our modern notions. Even our description of our brain has been shaped by his depiction of a human being. Certain regions of the brain have, until recently, been described as being largely devoted to sensory management and managing the basic works of keeping a body functioning, while the intellect was largely confined to the neocortex. Part of the brain has even been termed the ‘reptile brain’, which supposedly governs the most basic functions of living. Recent advances in mapping brain function are changing this conceptualization of how the brain works, and we know now that our thinking and other neural functions are distributed in complex manners. However the historical compartmentalizing of brain functions based on how our brain compares to that of more simple animals is in part due to Aquinas’s definition of a human.
