This question has challenged and entertained scientists and philosophers alike for ages and ages. If it has not yet been answered definitively, it can at least be addressed by delving briefly into the world of metaphysics. Metaphysics includes the study of transcendentals. It seems to be our universal nature to divide, categorize and name things for ease of understanding. In examining the question of “being”, we divide broadly into finite or infinite and then further divide the finite into more categories. Aristotle, (384–322 BC) enumerated ten unique categories for defining or describing the finite. Metaphysical transcendentals rise above all these divisions.
In the Middle Ages, philosopher and theologian Thomas Aquinas (1225 – 7 March 1274) argued that in all finite being the essence of a thing is distinct from its existence, that is, one can exist without the other. His contemporary, John Duns Scotus (c. 1266 – 8 November 1308) who is considered to be one of the three most important philosopher-theologians of the High Middle Ages, disagreed with Aquinas. Scotus argued that we cannot think about what it means to be something (essence), without also thinking about it as actually existing. So he developed and put forth his own theses.
Scotus did not believe that all created substances were simply composites of form and matter. He believed that matter exists that has no form at all and that a single substance can have more than one substantial form. He proposed an original princple called individuation, which speaks to the heart of our question. He drew a clear distiction between the common nature of beings, which would include features that would be found in any number of individuals and “haecceity” which is the specific combination of features that make one unique.
This question, posed by Scotus, is essentially the same question we are pondering here. Scotus asked, “What is it in this stone, by which as by a proximate foundation it is absolutely incompatible with the stone for it to be divided into several parts each of which is this stone, the kind of division that is proper to a universal whole as divided into its subjective parts?” Applied to the human person, he is asking what it is that ultimately unifies me into a unique individual, such that if removed, I would cease to exist? More simply, what defines the existence or non-existence of a specific individual?
Clearly, there was a time when I didn’t exist, but now I do. There is a saying that it is the clothes that make the man, but when I change my clothes during the day, I am not then a different individual. I am still the same person. If I wake up pale in the morning, spend the day at the beach and come home at night tanned, or more likely red, I am not thereby a different individual. I am still the same person. Even if I have organ transplants from another person, I am not a different individual. I am still the same person. My thoughts and emotions are essentially the same. Even if I change my mind and my attitude and my emotions, I am still me. How can I change so much and still continue to exist as the same person? What is that key element that makes me “me”?
What does science teach us about this? Can metaphysics explain it? How does the medical community weigh in? Is the key some thing learned or acquired or innate? Are there any answers or just more questions? Is there a knowable truth about our existence?