The classical Ship of Theseus paradox asks: if every component of a ship is replaced one by one, is it still the same ship? Or has it become something entirely different?
I'd like to reframe this question in neuroscientific terms to explore a profound issue of personal identity and continuity of self. Suppose we had the technological capacity to replace — one by one — every single neuron and glial cell in a human brain with perfectly functional artificial counterparts. These artificial neurons and glia behave identically to the biological originals: same electrical and chemical signaling, same integration into neural circuits, same plasticity, same responsiveness to input.
At every step, the individual retains memory, consciousness, personality, and subjective continuity. There is no noticeable disruption — either functionally or experientially. But at the end of the process, not a single biological cell remains.
So the question is: Is this still the same person? If yes, where does personal identity reside? If not, at what point during the process did the original person cease to exist?
This thought experiment invites contributions from various fields:
- Neuroscience: What does our current understanding of brain function suggest about such a transition?
- Philosophy of mind: What are the implications for consciousness, qualia, and the self?
- Computational neuroscience & AI: Is it enough to replicate function to preserve identity?
- Clinical & bioethical perspectives: What would this mean for brain-machine interfaces and future neuroengineering?
I would love to hear thoughts from neuroscientists, philosophers, cognitive scientists, engineers, and clinicians. Do you think this scenario leads to a gradual erasure of the original self, or to a continuous, intact survival of personal identity?
Why should anyone care, as long as it's a ship? I'd have thought that what matters is its properties to play the role of a ship, its similarity or not with some other particular ship shouldn't be relevant. The specifications of what's a ship don't rely in comparing two ships.
It's the history of an object or person that establishes a sense of identity of the particular object or person, distinguishing them from other objects or persons.
So a ship whose components have been replaced in some particular way is different from a ship, whose components have been replaced (or not) in another way. But it's the specifications that allow referring to both as ships at all.
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