Suppose some time in the future Humanity is able to map and mind-upload Human Brains, and that advances in AI had progressed to the point where it could be used to "experience subjectivity", Could the Qualia of differring subjective impressions be compared?

It might helpful to illustrate what I'm asking by using "The Butterfly Dream" of Taoist Philosopher Zhuangzi as an analogy. In it, Zhuangzi has a dream wherein he experiences the subjective impressions of a Butterfly. Of Couse it being an ancient anecdote, we can only speculate whether Zhuangzi's experience as a Butterfly had a different 'phenomenal character' than his prior and succeeding experiences as a human, and even whether 'novel' qualia than that which he had experienced previously (such as qualia related to the experience of flying) were actually present in constituting that dream experience.

So, in the same vein as Zhuangzi's experience of a butterfly, could a sufficiently intellgient AI likewise, compare the different phenomenal character's of uploaded brains, by 'experiencing' them firsthand? Could, by subjecting two or more uploaded brains to identical simulated stimuli, the ways in which phenomental experiences differ be identified, and if so, possibley even how the individual qualia of each brain's experience differ?

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    Zhuangzi's experience of a butterfly was Zhuangzi's experience of a butterfly, it was not butterfly's experience of a butterfly. The qualia were all Zhuangzi's, even if they were novel. Experiencing somebody else's qualia is an oxymoron, what can be shared through mind bridges or telepathy might be very exciting, but it will not, by definition, be subjective, and it will not, by definition, be qualia, regardless of technology used. In fact, twins with conjoined brains can "share mind" already today.
    – Conifold
    Commented Oct 8, 2020 at 7:57
  • @Conifold Would rephrasing "experiencing subjectivity" to "experiencing a subjectively produced experience" and rephrasing "qualia" to "elements that constitute, and characterise an experience" resolve this?
    – TomDot Com
    Commented Oct 8, 2020 at 8:29
  • Are there sharable aspects of experience that are currently inaccessible, but may become accessible with new technology? Sure, why not. But "subjectively produced" is ambiguous. Some "subjectively produced" music could not be produced, let alone shared, until synthesizers became available. People with brain damage could not share their "subjectively produced" impulses until they got brain implants. What matters is whether what is shared is private/phenomenal/qualia, not how it is produced. But whatever is shared will be phenomenalized by the receiver, and involve only their own qualia.
    – Conifold
    Commented Oct 8, 2020 at 8:50

3 Answers 3


Consciousnesses is phenomenon emerging from computation running in our brain (in the future also running on some hardware, computation itself is not substrate-dependent). We can theoretically determine, that two computations are exactly same. If two computings are different (either different algorithms, different data, or both), I don't think there is anything else to say about such two consciousnesses, beyond stating non-equality. It is hard to imagine any possibility of "description" of such complex computation. We can understand some computation of limited complexity. However, brain computation even in very simple organisms are far too complex. It is impossible to understand and "feel" functions, just by having blueprint of neural connections. Our comprehension capabilities are tiny for such task. Therefore, other neural computations, besides one's own, will very likely forever stay unreachable for humans. For AI, however, thing might be different. AIs theoretically might be capable to analyze and understand brain computation in great detail.


First, with the current knowledge in philosophy and neuroscience, I don’t think there’s a definite or unanimously-agreed answer to your question yet. So, the answer, which can only be deduced from current philosophical and neuroscientific knowledge, can only be an educated speculation.

Now, regarding your question, we have two ways to compare qualia of the same thing (such as visual qualia of the same house) in different persons or animals from two perspectives – the 1st person perspective and the 3rd person perspective.

The first way is to compare the qualia that occur in another person with the qualia that occur in you, by having experiences of both qualia by yourself and then comparing them. But, the only way to do this is for you to have an access to the qualia in the other person. Currently, this is not possible. Theoretically, it may be possible to access the qualia in the other person if there is a neural bridge that bridges the qualia-creating neural process (such as the visual-qualia-creating neural process – the final-step visual processing neural process??) in the other person to your consciousness neural process so that your consciousness can experience the qualia. The problems are, at present, we do not know exactly what and where the qualia-creating neural process for each kind of qualia (visual, auditory, olfactory, etc.) and the consciousness neural process are and we do not know how to make that neural bridge between them. So, practically, the possibility to compare qualia from the 1st person perspective seems to be very far off in the future.

What’s more, even if the bridge can be formed, there still is the problem of inevitable unidentical connections between the qualia-creating neural process and the two different consciousness neural processes because the two different consciousness neural processes, being separated, must be at different locations – rendering identical connections to the same qualia-creating neural process impossible. Consequently, the qualia may appear differently to the two consciousness neural processes in spite of being the same qualia. Thus, there is also this theoretical obstacle for the comparison of qualia from the 1st person perspective too.

Next, to compare qualia from the 3rd person perspective is to compare qualia in two or more persons from the perspective of the 3rd person who examines the qualia from the outside as an onlooker. Theoretically, this is possible if we know what qualia are physically (such as are some kind of signaling or information that are being sent out from the final sensory perception neural processes). We then examine and compare the physical parameters of the qualia in different persons. For example, if the visual qualia are the signaling of the final visual perception neural processes, we can compare parameters (e.g., the spatio-temproal parameters) of this signaling in different individuals to see if they are identical or not and can conclude from that physical comparison whether the qualia are identical or not.

The problems for this kind of comparison are, at present, we do not know exactly what qualia are physically or even whether they really are physical entities. However, currently, there are several neuroscientific theories positing what qualia are physically although none of them has been accepted widely as the correct one. For example, some theories assert that qualia are

  • a geometry of integrated information (1)
  • information cycled through a hierarchy of networks in a resonant state (2)
  • the spatial pattern of neuron's dendritic electrical activity (3)
  • a special kind of signaling pattern of neural processes (4)

Even if qualia are one of these physical entities, the problem of measuring and comparing these physical entities which involve the signaling of millions of neurons is certainly more than quite a daunting task and certainly not possible in the foreseeable future. Yet, despite this, if qualia really are physical entities, it must be possible to compare them from the 3rd person perspective, at least theoretically.


  1. Balduzzi D, Tononi G. Qualia: The geometry of integrated information. Friston KJ, editor. PLoS Comput Biol. 2009 Aug; 5(8): e1000462. DOI: 10.1371/journal.pcbi.1000462.

  2. Orpwood R. Information and the Origin of Qualia. Front Syst Neurosci. 2017Apr 21;11(Article 22):1-16. DOI: 10.3389/fnsys.2017.00022.

  3. Sevush S. Single-neuron Theory of Consciousness. Journal of Theoretical Biology. 2005.

  4. Ukachoke C. Theorem IV: A Quale is a Special Kind of Signaling Pattern In: The Basic Theory of the Mind. 1st ed. Bangkok, Thailand; Charansanitwong Printing Co. 2018.


It is quite possible to compare the neural signals of different individuals and to deduce what events they are experiencing, and some progress has been made in that direction.

But to directly access their subjective experiences - the qualia - of those events would be telepathy, and that is widely held not to be possible.

Even if the neural patterning were uploaded to a virtual world, the AI mind would have no knowledge as to the qualia experienced by the original human mind.

To take a more modern example than Zhuangzi's butterfly, certain species of octopus exhibit sentient behaviour. Their brains evolved entirely separately from ours, with our common ancestor probably being a flatworm. If you shine a dazzling light at one, its neural processing of the event will look very different from ours. So we have no idea how the quale of that experience feels to it; in imagining how it might feel, we are forced to invoke our own qualia.

So it is between individual people. Technically, they might vary every time we wake up but, because the quale of the memory and the quale of the current event have changed in synchrony, we are unaware of the overnight change. This may not matter at a practical level, being as far as science is concerned a purely metaphysical issue.

And that is the whole point - it is a metaphysical issue and not a scientific one.

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