Take a second out of your busy day and try to describe your conscious experience right now. I'll wait.
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Here's my own amateur attempt:
I can feel a bit of hair touching my forehead. I'm looking at a computer screen. I can hear the fridge buzzing behind me. I don't hear anything like inner speech going on inside my head, even though I'm typing. I can feel my socks on my feet. My neck is kind of sore.
Trying to isolate "what it's like" (in the sense philosophers of mind care about) is supposed to be easy, if you believe most philosophers. There's a whole philosophical tradition that takes our knowledge of the contents of our own consciousness to be clearer and more obvious than any knowledge we have of stuff outside our own consciousness (the chair I'm sitting on, the computer I'm typing on, etc.).
It's impossible to hang on to that idea after reading the interviews in this book, which are edited transcripts of interviews between Schwitzgebel (a philosopher) and Hurlburt (a psychologist) with "Melanie", a college graduate who has agreed to wear a beeper that beeps her at random times during the day, signaling her to record what she is experiencing during the moment just before the beep. In the interviews, Schwitzgebel and Hurlburt ask for clarification, press on certain details, and raise skeptical worries about what Melanie is reporting. It's absurdly fascinating.
My favorite example involves a discussion of Melanie's experience just before to a beep that sounded while she was reading a book about the German invasion of a Greek island in WWII. Here's Melanie:
Melanie: Okay, I was reading again. In this part of the book it was the arrival of the German invasion of the island. The line I was reading had to do with the arrival of a formation of Stukas--German planes. And so I had an image in my head, a really simple image, the kind that you get if you watch those World War II movies or footage from back then, of a line of military planes against a blue sky background with a couple of white clouds...
[Schwitzgebel and Hurlburt quiz her about this image: what angle does she see the planes from, etc. Then they ask her the following:]
Russ [Hurlburt]: And what does the plane in your image look like? Do you know what a Stuka is?
Melanie: I have no idea, so yeah, I kind of put in F-18s instead [laughs], because I make them up, so... (p. 108).
I found this exchange remarkable--what seemed like a totally normal description of a mental image turns, when pushed on slightly, into a bizarre composite of WWII and jet fighters, of some indeterminate level of detail (they don't press her on this, but what grounds does she have to think she's seeing F-18s, rather than F-14s, F-15s, F-16s, and so on?).
That's just one example of dozens of extremely interesting discussions about weird, idiosyncratic features of the subject's experience. It quickly becomes clear that there's constant confabulation, uncertainty, unconscious experimenter bias, lack of accurate terminology, and all kinds of other factors contributing to produce Melanie's descriptions.
There are theoretical glosses on what's going on by both Schwitzgebel and Hurlburt, but the interviews themselves are gripping and make the point that conscious experience is elusive more powerfully than any argument could. After reading this and Schwitzgebel's Perplexities of Consciousness, I think that he's doing the most gripping work in philosophy of mind right now.