One of my objectives was to show you can indeed deduce that other consciousness are real, and we can actually build theories even though it may seem we can only make individual conclusions at first.
A good example is the physical world. By the same logic, there would be no way to prove that anything at all outside your own subjective experience is real. There are many other possibilities that yield the same results and they yield identical results from first-hand experience. Yet, we don’t go (and shouldn’t for scientific beliefs as I’ll explain) about daily lives considering everyone else not to be real. That would at least lead us to treat everyone else extremely poorly at least when we have something to gain. We indeed make an estimate (not definite proof) that other people are real. This is an important observation of the disproof-impossibility, which I forgot to mention, that the correct logic for this formal systems is either some bayesian logic, or even some weaker versions of formality (that can be informally soft) that are easier to work with, at least until someone discovers better ways to formalize propositions with increasing rigor.
The objective of this comment isn’t to disprove solipsism (I will do so in a later post), but I believe to disprove it (in the soft, bayesian way indicated earlier) is that the arrangement necessary to provide a ‘solipsistic experience’ (i.e. a “personal universe” in which you are the only one existing, either through some kind of simulation or many other possibilities) should be much less likely to pan out considering all possible existences. It is necessary to engineer a highly sophisticated system to provide this illusion, which would be, certainly in our universe, astronomically costly and wholly infeasible. There are many more existences where you exist normally than where you exist “solipsistically”. This of course relies on a development of metaphysics (more precisely non-directly-observable physics), and I should have noted all of this in particular ethics has a critical dependence on this metaphysics.
Back to your objection, just like in other aspects of reality, the principle of continuity is likely to apply to consciousness. As a very first observation, note we can at least estimate two very similar brains and minds (in the sense of neural state, patterns and connectivity) should be experiencing similar qualia. To advance it to all minds, and how to estimate consciousness, would be a result of careful study and theory-building of many different minds (i.e. closely examine their neural patterns and associated behavior). From this study we will probably find many different interesting systems, structures and architectures. Suppose in general ways the architecture and patterns of your mind are similar enough to other people, with no drastic differences between them. Them invoking scientific principles like Occam’s razor, the Copernican Principle, etc. (also the principle of regularity I mentioned) we should both begin to understand the necessary elements for experiencing qualia and conclude other people than ourselves also experience qualia.
It would not only be extraordinary (in a scientific sense) to be the only person experiencing qualia (more so with other people even inventing the very concept!), but since our subjective experiences are part of reality and an emergent phenomenon, if you really were the only person experiencing qualia then something different in your neural patterns should be observed. Further investigation should yield several hypothesis, why not one of them, that only you experience sentience, and logical constraints I believe would finally show or associate this unique architecture, patterns or arrangement to be fundamental to sentience. Theoretically only of course, because scientifically this possibility would be both extraordinary and absurd (very unlikely at a first estimate).
Thank you for your comment :)
It’s this kind of problem that this theory tries to address. What you have to do, essentially, is study the brains and neural patterns of individuals to understand the nature of, if not qualia in general, at least some qualia, and understand some of the features of consciousness.
It’s also not like self-reporting is totally useless. If someone declares not to feel pain, or joy, or some other set of emotions, I would be inclined to believe them or suspect there might be some different experience going on for them. Notably, people report not experiencing visual images in their conscious minds (aphantasia), and this is not difficult to believe and well studied. I believe there have been neuroscientific studies involved. You may be able to show for example the circuits involved with conjuring visual pictures are not present or different for those individuals. So you start from a hypothesis and confirm it using neuroscientific tools. At a formal level, you might be able to prove that, in the absence of some circuit to generate and integrate visual information based on their neural circuitry, some people provably can’t conjure images in their minds in a particular sense. That means you’ve proven something about a mind through scientific means, a scientific window into subjectivity. We can develop many such tools and I believe in the limit we should be able to, at least in theory, understand and map out every qualia, and the nature of consciousness itself.
I agree that there’s some inherent unreliability and suspiciousness to this process. The necessary elements to experience qualia or consciousness, etc.. may be very particular and we might miss their fundamental mechanisms—for example, maybe some people report experiencing qualia in general or having particular qualia while having significantly different or reduced qualia in certain sense. But I don’t think there’s a large enough chance for this to happen to discredit the whole approach. In most likelihood, most people that report being consciousness are probably conscious, and studying our minds will probably, again at least in theory, yield the correct understanding of what those things really are in the scientific sense.
Another example is AI. You can more or less easily train even extremely advanced AI to virtually always say it is either conscious or totally unconscious. By default, for instance a Large Language Model, will reproduce the training data patterns, generated by humans, that usually claim to be fully conscious and of course experiencing human-like qualia. That’s to say taking beings in general for what they say is again suspicious. But that’s not our only tool (self-reporting), the self-reporting is only a suggestion and starting point to look at neural circuits and reverse engineer our minds in such a way to hopefully discover and map out what consciousness/qualia really is, what differences there might be between individuals, and so on.
Edit: You may also use self-reporting to map out detailed features of our experiences, and then find neural correlates and study those neural correlates. Here I am inclined to agree with @Dagon that sentience and qualia isn’t one thing, but rather a zoo of experiences that manifest as subjective phenomena. All however share this fundamental property of subjective manifestation in the first place (that is, being a thing that is indeed experienced in our minds).
The ultimate application is of course always: how can we use this knowledge to live better lives. In theory, as you map out properties of experiences, that allows a basis to try and understand (using those very same tools) what makes one qualia good and another bad (e.g. deep suffering versus that meaningful and uniquely joyous moment in your life). We get a better grip on what kind of art should we make, what culture should we produce, how can we live better lives in general.
Moreover, the mere existence of this possibility to me helps invalidate notions I commonly see that deny any sense of universal ethics, that claim ethics is just an arbitrary invention or accident, that power for the sake of power ought to be our end goal, that reproduction ought to be our end goal, that each individual must build a completely personal and unique theory of meaning (or die trying!), among several variations. There is a whole world of despair readily found based on those conceptions, which I believe are seriously harmful and in a sense provably false.
The existence of a basis for ethics, based on experiences (qualia/consciousness/sentience), is already very philosophically compelling and helpful for very many people I believe.