Scientific study of consciousness comes from ignoring our subjective impressions of our own consciousnesses, which might be illusory, and going only by what can be seen by other people. So you have experiments doing things like showing subjects subliminal images trying to probe the boundaries between conscious experience and unconscious experience. You start with results like "If we show this image to subjects for 50 ms it only has a slight effect on their behavior which fades out after a second, but if we show it to them for 60 ms it has a large effect for the rest of the experiment including being able to talk about it" and then you keep going from there.

> I know exactly what consciousness is based on my experience with it, even though I could not possibly give a comprehensive account of everything consciousness entails.

Not sure if personal experiences count. Generally, we laugh at people who talk about esoteric experiences.

So a simple explanation could be that consciousness is an illusion?

Or put differently, is there any phenomenon that needs the assumption of consciousness?

The way I experience myself could be just the history of experiences. So there is something that the brain can refer to.

> I know exactly what consciousness is based on my experience with it, even though I could not possibly give a comprehensive account of everything consciousness entails.

What is the price of that kind of knowledge? You don't even know where is the border between your knowledge and your absence of knowledge. How much can you tell about consciousness without stepping on "absence of knowledge" field? Pretty nothing, isn't it?

> By analogy, I've been married for just shy of 20 years. I know my wife very well. I certainly do not know everything there is to know about her, but I do know her.

I have a better example. I speak English for 20 years if to start counting from my first English lesson when I learned my first English word. You can find plenty of silly mistakes in my comments. But at least I know what I can express or understand and what I can not.

> I know exactly what consciousness is based on my experience with it

OK, then what is it?