What is consciousness?

Hemispherectomy is a radical and fascinating surgical procedure where half of a person’s brain is removed. This surgery is typically performed on very young children, whose brains are still plastic and adaptable enough to reassign the functions of the removed hemisphere to the remaining half. Often, this procedure is a last resort for managing severe, drug-resistant seizures originating from one side of the brain.

But here's a mind-bending question: if you can live with just half a brain, what would happen if we took two empty skulls, split your brain down the middle, and placed each half into a separate body? Which of these new individuals would truly be you? This question digs deep into the nature of consciousness and personal identity.

To understand this, we must explore what makes you uniquely you. It’s not just about having thoughts or experiences—though these are crucial. Instead, it's about your sense of self. When you think about what it feels like to be you, it seems like you’re an observer inside your body, looking out through your eyes. This subjective experience, your personal awareness of your thoughts and feelings, is what we call consciousness.

But if your brain were split and placed into two different bodies, would both of these new people possess consciousness? Or would only one truly be you, while the other would be a new, separate person with its own sense of self?

To grapple with these questions, let’s start by considering what we know about consciousness—or rather, what we know about things that are not conscious. Take Cleverbot, for instance. Cleverbot.com is an AI chatbot that can cleverly respond to questions. However, Cleverbot is not conscious; it doesn’t have a sense of self or personal experiences. It’s merely a program reacting to inputs, without any awareness or inner life.

Now, compare Cleverbot to yourself. You know you have thoughts and feelings, and you have a sense of yourself as a distinct, conscious being. But how can you be sure that others share this same quality of consciousness? How can you be certain that everyone you interact with isn’t just a sophisticated version of Cleverbot, responding automatically without genuine awareness?

This question touches on a profound philosophical issue: the concept of the “philosophical zombie.” A philosophical zombie is a hypothetical being that behaves exactly like a human but lacks consciousness. It would react and respond as if it were conscious, but it would have no inner experience or awareness. This concept challenges our understanding of consciousness and raises the question of whether it is possible for someone to appear conscious without actually being so.

Interestingly, science has yet to provide a clear answer to this question. While we study various disorders of consciousness, such as anosognosia and Anton-Babinski Syndrome, we still lack a definitive understanding of consciousness itself.

Anosognosia is a condition where patients are unaware of their disabilities. For instance, a person who has lost the ability to move a limb might still claim they can move it and offer confabulated explanations for why it’s not moving. Similarly, Anton-Babinski Syndrome involves patients who are blind but deny their blindness, making excuses for their inability to see.

These conditions reveal a disconnect between what patients truly experience and their conscious awareness. They highlight how our understanding of consciousness is still incomplete, as we can observe discrepancies between a person’s physical state and their self-reported experience.

Moreover, philosophical thought experiments like the “Swampman” further complicate our understanding of personal identity and consciousness. Imagine if, after being struck by lightning and disintegrated, a second lightning bolt rearranged atoms to form an exact replica of you. Would this new entity be you, or merely a copy?

Similarly, consider a scenario where a surgeon gradually replaces your cells with those of another person, one cell at a time. At what point would you become that other person? These questions challenge our notions of identity and consciousness, revealing how difficult it is to pinpoint what truly makes us who we are.

Despite the lack of definitive answers, these thought experiments and philosophical inquiries encourage us to explore the nature of consciousness and personal identity. They invite us to reflect on what it means to be truly aware and to question the very essence of our existence. In the end, while we may not have all the answers, the journey into these profound questions can lead to a deeper understanding of ourselves and the world around us.