A primer on consciousness

An overview of a problem I've long been obsessed with.

There are questions that organize our lives, whether we ever ask them or not. Here's one: how is it possible that matter gives rise to consciousness?

I vividly remember the first time I stumbled upon these words, and the feeling of astonishment that accompanied them. On an otherwise unremarkable weekday a few years ago, I stood in the kitchenette of my office and was transfixed by the question of how inanimate, nonconscious matter could give rise to conscious experiences.

Whether you find this question mundane, mildly interesting, or mind-boggling depends on your worldview: the assumptions you make about what reality is made of. In this post, I'll talk about various philosophical stances one can take on consciousness and reality, and how my own views have changed over time.

What is consciousness?

First we need to agree about what we're pointing to when we use the word "consciousness". I'll define consciousness to be the same thing as subjective experience. To be conscious is to have some kind of subjective experience, regardless of how complex or simple that experience is. A human experiences things, while a chair does not.

To say that an entity is conscious (say, a bat) is to say that there's something that it's like to be that bat. The bat is aware of something; the lights are on in the bat's mind.

Note that in this definition, consciousness is not the same as self-awareness. The self is just one thing that you can be aware of, but you can be conscious even without being aware of your self (e.g. in a flow state, or a deep meditative experience). Consciousness is also not the same as thinking: you are conscious of much more than your thoughts, and you can be conscious of many things (like sights and smells) without thinking about them.


I came into the question of consciousness from a materialist worldview. If someone asked me to paint a picture of the fundamental nature of reality, I would have said something like this: reality, at its core, is mostly dark and mostly empty space. Interspersed in this empty space are little spherical objects called atoms, which have mass and move around, and these atoms are made of protons and neutrons and electrons, which are themselves little spherical objects with mass that move around.

These building blocks are effectively automata: they are non-sentient particles that move according to deterministic laws of physics. The particles come together to form all the things we see in our everyday experience like chairs, dogs, and humans. And astoundingly, some of those everyday objects feel things, even though their constituent parts – the atoms – do not feel things.

How could it possibly be that a particular configuration of nonconscious particles generates subjective experiences? Looking at the brain, why would a particular pattern of excitation of neurons—which is really just ions moving back and forth across a cell membrane—produce the color red, or the smell of garlic, or the sound of the violin? And what is it about those configurations that explains the nature of different experiences: the fact that sounds have a particular subjective quality while smells are markedly different?

The hard problem

The above question is what philosopher David Chalmers calls the "hard problem" of consciousness. Chalmers claims that consciousness poses a particularly difficult problem unlike anything else we've attempted to understand, including problems like the brain's ability to process stimuli, learn, and make decisions.

The crucial difference between these "easier" problems (perception, intelligence, learning) and the problem of consciousness is this: we have some sense as to how the movement of tiny particles could result in things like information processing or decision-making or even intelligence. Even though we're not close to actually understanding intelligence and agency, it seems plausible that all you need in order to get a system with those properties is to have all the right particles moving in the right ways at the right times.1 We can imagine entities that do all of this computation and information-processing but which are not conscious. So why and how does consciousness arise at all?

Here's another framing of the hard problem: why does the pattern of fluctuations of photons and neural action potentials give us the particular spectrum of colors that we see on a fruit plate, rather than an "inverted" spectrum like the picture on the right? The two are functionally equivalent, but are totally different qualitative experiences.

While we can explain self-replication, information processing, and pretty much everything else about life and the universe via extrinsic, functional descriptions of the movement of things, explaining consciousness would have to involve more than just an extrinsic description. A theory of consciousness would have to explain the relationship between extrinsic properties—the things we can observe—and internal experience, which is something that seems impossible to access "from the outside".

Confronting the hard problem

Philosophers and neuroscientists have taken many different approaches to tackling the hard problem. Some deny that there is a hard problem at all, either by claiming that consciousness is an illusion (and thus not in need of explanation), or by claiming that there is no special explanatory gap when jumping from nonconscious matter to conscious experience.2

Alternatively, some have taken the hard problem seriously, and have begun to question the metaphysical assumptions that generate it. I mentioned above that objects like chairs and atoms don't have conscious experiences. Do we actually know that they don't? The only way we really "measure" consciousness in others is...by asking them.3 But we know that the inability to report a subjective experience is not the same thing as not having one. (Case in point: locked-in syndrome.)

Another way we "measure" consciousness is by making analogies between the human brain and other systems that process information in similar ways (like the nervous systems of other mammals). But even here, it's difficult to tell how much similarity is "enough" for consciousness when we don’t have a causal explanation.

Are plants conscious? While they don't have full-fledged nervous systems, they do appear to have similar mechanisms as mammals for sensory processing, intercellular communication via ion channels, and even memory formation. (See the book What a Plant Knows.) How do we know whether or not this leads to consciousness?


One way to resolve the hard problem is to claim that the notion of non-sentient, non-feeling matter was mistaken to begin with. Rather than consciousness emerging from the movement of unconscious atoms, perhaps consciousness is built into the fabric of reality. This is a family of views called panpsychism. There are many variants of it, but here are two theories I find intriguing:

To be clear, what scholars like Kastrup and Hoffman are proposing (and they're proposing slightly different things) is not that, for example, chairs have complex inner lives and actually feel our presence when we sit on them. It's more that somehow, what appears to us as a chair is a byproduct of a conscious process. If we were to dig deeper and deeper into the make-up of the chair, rather than finding total non-awareness, we might instead find a much more primitive awareness than what we're used to.

Bernardo Kastrup argues that one of the conceptual advantages of the view that “reality is mental” is parsimony. Unlike materialism, which posits the existence of two fundamentally distinct entities in the universe (consciousness and matter), analytic idealism proposes just one.

Other approaches

Understandably, some scholars find panpsychism to be far-fetched, and have attempted to formulate other theories to explain consciousness. Some argue that consciousness is tied to integrated information processing, or to minimizing free energy, or to the evolutionary imperative for adaptive movement. Others believe that the best way to understand consciousness is to drop all the philosophizing and just understand the brain better. And still others believe that the truly mysterious entity in need of further explanation is not consciousness, but matter.

Clearly, no one knows the answer just yet. We may be close, or we may have framed the question in a way that makes it impossible to solve. Over the course of my own explorations into the topic, my intuitions have shifted again and again. At one point I was convinced that consciousness must be fundamental to reality, while at other points I've had the sense that it probably just arises from complex information processing. And I'm open to the view that perhaps consciousness isn't just one thing but a whole collection of separable things, and that we can make progress by studying those parts individually.

But there’s one thing hasn't changed throughout this exploration: whenever I take note of the fact that I am a conscious being in this universe, I'm left in a state of awe. Thinking and reading about consciousness has only deepened my appreciation for the mystery and profundity of the one thing you can always be sure of. Whatever is going on in the world, whatever reality is actually made of, there is something that it's like to be you.


The opening quote is taken from a lesson in the Waking Up meditation app.

For a concise overview of the problem of consciousness, see Conscious by Annaka Harris.

For a few extra notes to this piece, see this.


Of course, this isn't to say that it's actually easy to solve these other problems. Chalmers' point (and I agree with him) is that these problems do not pose the same conceptual hurdle that consciousness does.


I'm personally quite convinced that consciousness is not an illusion and that there really is a hard problem, so I may be misrepresenting the opposing view here.


As in, we discern whether someone's conscious (and what they're conscious of) by having them respond to certain stimuli and prompts.