Do I have a spirit, soul, or some other metaphysical identity?
Am I just a series of biological processes which create the illusion of consciousness?
Scientifically, the human brain is causally closed, which means that we can identify the beginning, middle and end of all conscious processes via neurons. We can explain how consciousness arises - so the need for a supernatural self is redundant.
And yet, I have the prevailing sense that "I" exist. Whether I'm thinking, talking, dreaming, writing or walking, it feels as if the experience is happening to "me". Therein lies the problem. Scientific observation tells us there is no need for a self, but the experience of being human most definitely feels like there is something more to it.
To solve this problem, philosophers have devised a number of theories of the self. These are categorized in two groups: bundle theory and ego theory...
Bundle theory says that the self doesn't arise from an enduring "I" but rather from packets of individual experiences over time. In other words, your whole life is a series of events that occur in sequential bundles - but there is no single consciousness that can lay claim to experiencing all these events in your life.
While scientific in its founding logic, the Buddha probably created the first bundle theory. Among the world's religions, Buddhism alone rejects the idea of the self. According to the legend, some 2,500 years ago the Buddha became enlightened after a long meditation under a tree. He rejected the idea of the eternal inner self and embraced the notion of no-self. He taught that much human suffering is caused by clinging to the idea of the self and that we should aim to shed this intuitive interpretation of our experience of consciousness.
Bundle theory is difficult to accept in our heart-of-hearts because it conflicts with our intuition. But it does have the backing of some of history's most famous philosophers (notably David Hume in the 18th century) and does a very good job of explaining the illusion of the self, both philosophically and biologically.
In contrast, ego theory is based on the existence of a persistent self.
It lives in many forms. Supernatural theories rely on the existence of a spirit or eternal soul (this is central to the religious beliefs of Christians, Jews, Muslims and Hindus). Scientific theories rely on locating enduring structures in the brain which might give rise to a continuous self.
Ego theorists point to split-brain patients as evidence of this. In the 1950s and 60s, many epileptic patients had their brains almost completely severed in two, in an attempt to stop seizures spreading from one hemisphere to the other. While most recovered very well, retaining their pre-surgery IQ and personality, they did show some peculiar "dual-self" traits.
For instance, if you briefly showed a snow scene to the right hemisphere (via the left visual field) and a chicken claw to the left (via the right visual field) the patient would verbally report only seeing a chicken claw, because the left hemisphere dominates language. When subsequently asked to match what they saw to an image, the left hand pointed out a shovel to shift the snow - the right hemisphere now linking the images together conceptually.
It was as if the split-brain patients had two separate streams of consciousness, unified by the hemisphere's individual responses to different packets of stimuli. Two selves; one person.
In response to this, bundle theorists point out that it violates Ockham's Razor (where the observed minimalist solution is always better than calling upon additional unknown factors). What's more, we can have several states of awareness of several different experiences at once in a single brain; it still doesn't prove the existence of an enduring self.
There is a famous thought experiment which will help you decide which view you currently subscribe to. In fact... it may even make you change your mind.
Imagine a teleporter that is 100% proven and safe. It works by scanning every atom in your body, destroying you, and instantly recreating you atom-by-atom at your destination. The process is totally painless and you'll still have all your memories intact when you emerge the other end.
Would you use it?
Bundle theorists would have no hesitation. Every biological structure in your body will be exactly the same at the other end. No-one will be able to tell the difference - not even you, because the illusion of the self remains.
Ego theorists would stay the heck out of that teleporter. Not only would they be dead, but the soul-less creature that emerged the other side would be an artificial clone of them; a zombie with no inner self.
So far the consensus is that we all have a sense of self, but opinions differ on the true origins of this self. Is it biological or metaphysical (real, existing in a form we are yet to validate scientifically) or psychological (a mental illusion; non-existent)?
It may help if we ask the question: exactly what is the self? The answer may lie in our understanding of human consciousness.
In laymen everywhere, the most intuitive way of viewing consciousness invokes ego theory, as if the human mind is a private theater. As a spectator, I am sitting inside my own head, looking out through my eyes. My senses also allow me to hear, touch, taste and smell the events of the outside world. I can even invoke my own imagination internally by conjuring new or remembered stimulus in my mind's eye.
Though it feels like an adequate description of consciousness as we experience it, there are some major flaws with this conceptualization. And they throw our whole understanding of consciousness out the window.
The Cartesian theater of the mind is based on Rene Descartes' famous dualism theory from the 17th century. Dualism states that the mind and the body function as separate things. According to Descartes, the mind is non-physical and has no actual position inside the head. Yet it is still a real, independent structure.
The problem with dualism, as the philosopher Daniel Dennett points out, is that there is no known mechanism for an ethereal mind to communicate with the physical brain. Descartes pointed to the tiny pineal gland in the center of the brain as a possible meeting point, but this is purely speculative. Without this conduit, the mind can't be "real" as Descartes stated. And neither can dualism.
Dennett also rejects the Cartesian theater on the basis that there is no central headquarters of the brain via which all conscious information is processed. The brain is a parallel processing system, distributing sensory information across a network. Like bees in a beehive, countless elements get on with their own jobs, communicating individually as needed, to complete a single major task as a whole.
Even if we ditch the theater analogy, it still doesn't help us understand why consciousness feels like a single unified stream of awareness. There is no all-seeing-eye in the neural network; no grand observer in the massive web of interactions. Mind boggling as it is, the idea that all my thoughts and experiences are funneled through a single observer is simply... wrong.
Today, the scientific community formally rejects dualism as an explanation for consciousness and the self. But it's an important point to raise; after all, it is the most intuitive explanation for our sense of selves, and the majority of people from all different backgrounds subscribe to the notion, albeit unknowingly.
Dennett created the term Cartesian materialist to describe people who logically reject dualism, but cling to the idea of a separate self. It's an awkward admission for a scientist to formally reject a theory, yet still subscribe to its conclusion. Indeed, most scientists won't admit to being Cartesian materialists. Yet as we can see from many popular ego theories around today, the underlying idea of a "theater of the mind" or a "stream of consciousness" still holds strong.
So the sense of self is still very much alive and kicking, even when the supporting evidence suggests it is merely an illusion that we can't explain...