Lately I've been thinking a lot about consciousness. What it is, what it means, how ubiquitous it is, and the ethical implications of all that. Broadly, I think I would define a conscious being as a part of the universe that is capable of experiencing itself, as well as other parts of the universe.
To backtrack a little though, I do think many parts of the universe are non-conscious. Rocks, for example. I don't think rocks have any particular internal experience, and even if I did believe that I'd have no way to empirically prove that. However there are many parts of the universe that do provably have internal experience, namely those that exhibit experience-sensitive behavior. If something is capable of behavior, and alters that behavior in response to particular environmental stimuli, it can confidently be said to have some degree of internal experience.
Those parts that do experience exist along a spectrum of consciousness. The level of consciousness in a human is different from the level of consciousness in a worm, which is different from the level of consciousness in, say, a fern. While all can be said to have internal experience (or, if we use the term broadly, consciousness) in one form or another, they are all so vastly different that their experiences are not meaningfully comparable. The similarity though that distinguishes conscious from non-conscious beings is that conscious beings perceive; they all have some way of sensing themselves in relation to other parts of the universe. Whereas non-conscious parts of the universe exist in a state of total non-awareness.
At the moment, I am leaning towards the idea that what separates one conscious individual from another conscious individual is literally just perceptual experience. The only difference between me and you is that we perceive differently. I think it's also worth noting here that I would consider complex thought to be a form of meta-perception, or perception of perceptions. All thoughts are at the end of the day rooted in perception or observation. The mind can be considered a sensory organ in and of itself, one which perceives not just sound or vision or scent in the rest of the world but rather the particular experiences observed by the other sensory organs. Taking this into consideration, the interpretations we have about the world, the ways we feel about ourselves, and the behavioral patterns we exhibit are all products of perception and perception alone.
This all ties into the idea that our sense of self is an illusion. There is no fundamental difference between me and any other person. There is no clear boundary where I end and they begin. My sense of my self as a concrete thing that is separate from the rest of the world, my idea that there is some division between the internal and the external worlds, is quite simply false. The universe is one being with many different aspects, and those aspects are fundamentally limited in their perceptions. One conscious being, one aspect of the universe, simply cannot perceive the universe in its entirety. Because consciousness is perception, it necessitates perspective. And total perception of the universe necessitates a lack of perspective. Total awareness and consciousness are, therefore, incompatible.