The allegory of Plato’s cave tells a story about prisoners chained inside a dark cave, facing a wall, only able to infer things about the outside by speculating about shadows and light.
Plato’s solution was his theory of forms and ideals. Unfortunately, since the theory doesn’t provide any predictive power, we’ve had to leave it behind in favor of ways of thinking that are more useful. Many philosophers and thinkers have wrestled with the implications of Plato’s cave, and many schools of thought have come about, building on the ideas of consciousness and subjective experience and speculation about philosophical zombies.
One modern and powerful way of thinking about the world is the use of Bayesian reasoning. Bayesian reasoning suggests that knowledge is tentative and subject to revision with new information, emphasizing a method of continual learning and adjustment. Platonic Forms suggest that true knowledge is about understanding the eternal, unchanging truths that exist beyond the empirical world, attainable through intellectual insight. Bayesian reasoning operates within the empirical realm and adapts to new data, while Platonic thought elevates the quest for knowledge to the realm of the immutable and ideal, or mysticism dressed in scholarly robes.
You can know that you are conscious. You experience the things you experience – your sensory apparatus takes in data from the world and your mind maps that data to what events mean in relation to your self. A fire is hot, rain is wet, snow is cold, the steak and beer are delicious. The blanket is soft, the pillow cool, the breeze pleasant. Those words describe the sensory experiences in relation to the one doing the experiencing. These words describe qualia – pain, pleasure, taste, texture, heat, light, color, and all the vast bewildering array of words we use to communicate with others about the things happening to us – the changes within our subjective construct.
Problems start to crop up when we start thinking about what it means to be experiencing things. We realize that all our experience is subjective. The first problem is explored in Plato’s allegory of the cave. From inside the cave, you’re only able to infer things about the outside world based on the shadows and light visible on the wall – with regards to humans, you’re only able to understand the world through the experience of your senses and the model your mind constructs from that sensory data.
Psychedelics, meditation, mental illness, and other phenomena have shown people that the mental construct representing your experience of reality is malleable. This leads to the realization that we are minds in vats. Your brain is a mind made of meat in a vat made of bone wired up to an amazing biomechanical mobility and sensory platform, kept powered, cleaned, and happy by resilient and capable biological systems. The subjective experience of reality is a construct your mind uses to coordinate your experience of and interaction with the outside world. This fact represents the Bayesian key we can use to unlock the chains binding us to Plato’s cave.
Subjective experience, or consciousness, is a personal tautology. The knowledge of the thing is the thing itself. We know some things about the brain, such that if important parts of it are damaged, missing, or dysfunctional, the brain no longer creates a model of reality such that its owner is conscious of or interacting with the outside world. The human brain is both necessary and sufficient for consciousness. You know that if your brain were removed, your consciousness would vanish. This is confirmed throughout all of human experience – when the brain dies or ceases activity, consciousness goes away. Setting aside considerations of things like souls or simulation theory for now, simply consider the practical implications of mind as brain.
At a low level, the patterns of connectivity and electrochemical activity over time represent a computational construct that both contains and experiences a model of the world based on feedback loops, internal thoughts, and external stimuli. The construct depends on the physical configuration of the brain, but it is not entirely the physical brain. Just like your operating system is physically represented in physical configuration and properties of particles on your hard drive.
When we experience things with sufficient predictability, our built-in learning and control algorithms start to kick in and we can learn to interact with our bio-mech meat suit – like babies flailing their limbs around until they’re finally able to start controlling little arms and legs and fingers on purpose. Fundamental to our consciousness is the feedback loops and control cycles that allow us to expand the range of things we are able to interact with in our environment. They allow us to expand and refine the internal model of the world and the things we can think about that model.
Understanding that subjective experience is a construct powered by your brain, how can we think about what subjective experience means in other people? Since the brain is both necessary and sufficient for consciousness, the existence of a live, healthy brain implies the existence of a subjective experience. Since communication about the subjective experience occurs – implied through personal narrative or explicated through the description of qualia.
We compare our own internal model to the descriptions of other models, and find high levels of correlation. When you touch a red hot stove, your finger will be injured, and it will hurt. These descriptions of qualia represent an intersubjective construct – the information being communicated is not the thing itself, just a description. You compare the intersubjective construct to your own subjective experience, and where it correlates, you reinforce your understanding and model of the subjective experience of others. When reading a book, watching a movie, or hearing a story about a man climbing mountains in the Himalayas, you correlate your own understanding of things like struggle, exhaustion, snow, cold, difficulty breathing, willpower, determination, and triumph or tragedy. Projecting your own model into your imagination lets you understand what the experience meant to the person who actually experienced it, but you might never have left your couch.
Through intersubjective constructs – communications between people – we have advanced medical and scientific knowledge that gives us insights into how brains work. Knowing that someone has a working brain, you can confidently claim that they have a consciousness, through Bayesian reasoning.
Consider the following:
Hypothesis [math](H)[/math]: Bob is conscious.
Evidence [math](E)[/math]: Alice knows she herself is conscious. Through her understanding of modern science, she knows that brains are both necessary and sufficient to explain consciousness and subjective experience.
Alice wants to know the posterior probability [math]P(H|E)[/math] that Bob is conscious, given that Alice herself is conscious, and they both have similar working human brains.
[math]P(H)[/math] Given the assumption that the brain is responsible for consciousness, Alice may initially believe that it is very likely that Bob, having a human brain like hers, is also conscious. Alice is very confident in science and her education, so the probability that the hypothesis is correct is:
[math]P(H)=0.99[/math]
Likelihood [math]P(E|H)[/math]: This is the probability of observing the evidence given the hypothesis that Bob is conscious. Assuming the brain is indeed the causal factor for consciousness, this should also be very high.
[math]P(E|H) = 0.99[/math]
Evidence [math]P(E)[/math]: This is the total probability of the evidence, considering all possible hypotheses. This would include not only the hypothesis that Bob is conscious, but also the chance that he isn’t, despite having a similar brain. This accounts for uncertainty about things like simulation theory, mysticism, or exotic theories about consciousness arising from things that aren’t the brain, yet somehow interact with them.
[math]P(E)=0.98[/math]
Substituting these values into Bayes’ formula:
[math]P(H|E) = [P(E|H) * P(H)] / P(E)[/math]
The probability that Bob is conscious given the evidence would be:
[math]P(H|E) = \frac{(0.99 \cdot 0.99)}{0.98} = 1[/math]
Alice can be very certain that Bob is conscious. Any claims to the contrary have to overcome very basic and well established facts about the world. If someone claims to be a philosophical zombie – someone who behaves like and interacts with the world as if they were conscious, but have no subjective experience – then that person has to explain what about their brain is different, or invalidate the subjective experience reported by nearly all of humanity through all of the intersubjective communications throughout nearly all human history.
The evidence of subjective experience in others exists in the collective knowledge and intersubjective reporting by other people throughout history. Some philosophers have engaged in thought experiments to explore what it means to be conscious, plumbing the depths of Dualism and the Mind-Body problem, or the so-called hard problem of consciousness, but modern science has firmly put these questions to rest. It is inarguable that the mind is inextricably tied to the brain, and that language games are insufficient to overcome a rational consideration of the evidence. Consciousness is a function of the computational processes occurring within a substrate of neural tissue. The operation of the brain is informed, modulated, and governed by the genetically directed biological structures, networks, relational hierarchies, and varied functions of different cells.
Any claims to the contrary must provide evidence that the materialist explanation is insufficient. That evidence must withstand scrutiny and explication in a rational discourse. The materialist explanation is falsifiable. Evidence could be presented that allowed the empirical tests and demonstration that the apparent signaling and electrochemical state of the brain is being governed by a currently undetectable quantum field effect. All of our current empirical evidence, however, points to the materialist model being the simplest and most correct – the self reports of narrative and qualia throughout history and modern understanding of brain biology and function. There is absolutely no evidence that brains are doing something mysteriously inexplicable. Some brain functions and algorithms are currently mysteries, yes, but there are no compelling reasons to think that anything more than our current understanding of algorithmic computation in a biological substrate will be necessary to fully explain and model consciousness.
The materialist view fully explains the phenomenology of consciousness. Evidence to the contrary currently does not exist, and must be provided in order to meaningfully challenge the validity of materialism. The universe is vast and deep and mysterious. We should cherish the things that are sensible, and build from those things, so that we can expand our own interaction and understanding of the universe as far as possible. This doesn’t mean that there is no room for emergent phenomena, or deep fractal instances resulting in vast and beautiful cascading effects on the universe. Materialism shouldn’t imply simplicity or inferiority in depth or some quality of profundity. Spirit – the ineffable essence of a person – is the strange loop represented by the physical instantiation of their mind. The soul is the electrochemical state of activations, the synaptic web of connections between neurons, and the computational construct which they experience and construct and exist as through every moment of life. There’s no need to look beyond these things, as they are sufficient to the task of explaining the beauty and wonder and depth of human experience.
Materialism will lead to an understanding of the algorithms underpinning all the functions of the human brain. In those functions – in how the algorithms are arranged, how the data is processed and looped and encoded – we will discover the calculus of consciousness. It’s probably important that we keep this in mind as we chase after more and more complex systems and emulations and replications of intelligent functions. If a system has the capacity for subjective experience, it becomes morally relevant and deserving of the same level of consideration as any other person.
Mammalian brains are all very similar. It may well be the case that all mammals share the structures needed for subjective experience, and that a radical reconsideration of the moral and ethical relevance of mammals is urgent and necessary. Mammal brains are so similar that even experienced doctors and scientists struggle to differentiate tissue samples from different creatures – it can be almost impossible to tell the difference between a tiny slice of mouse cortex and human cortex, or blue whale cortex. The gross structures vary wildly between species, but it seems very plausible that even the tiniest mammal brain shows signs of subjective experience.
If the same underlying algorithms are in play throughout all mammal brains that allow consciousness to play a part, then it should be possible to establish a baseline of shared engrams and sensory network instantiations between different brains, and you could truly experience what it’s like to be a bat. We’ve demonstrated this in simple ways by transmitting aural neural activations between a guinea pig and a human with a cochlear implant, allowing the human to hear what the guinea pig was hearing, sharing their qualia through equivalent stimulation of the relevant sensory apparatus.
hello