Characterizing a subjective experience is not the same as experiencing the phenomena. If I look at brainwave data of a monk meditating, my experience is of looking at and interpreting data. I am not meditating.
The canonical thought experiment from philosophy is called "The Knowledge Argument". In it, you are asked to imagine a super-intelligent but color-blind since birth scientist named Mary who knows everything there is to know about human perception from a scientific point of view. (Btw, she's completely color-blind; she only sees in black & white.) Since she knows everything there is to know, surely she knows what it's like to see the color red, right?
On the other hand, we feel pretty confident that when she is cured of her color-blindness and is then handed a ripe tomato, she'll say, "OMFG! I never imagined that red would like like that!"
So one possible conclusion from this is that it is impossible to know everything (that can be known) scientifically.
"Mary who knows everything there is to know about human perception from a scientific point of view. ... Since she knows everything there is to know"
The second assertion does not necessarily follow from the first.
There may well be more to understanding something than what science can know about it.
Also, there's something that analytic philosophers like to call "qualia", which is what it's like to experience something. That's one thing that would be missing from the above account.
To take another example: I could know quite a lot about the neurological processes that underly the sensation of pain in the human nervous system and the brain. However, such knowledge is very different from the sensation of pain itself.
Same with sex. You can read up about its physiology all you like, but your knowledge of it is going to be of a quite different order from someone who's actually had sex.
> There may well be more to understanding something than what science can know about it.
I'm pretty sure I mentioned that. But who knows? Maybe I just did too much acid back in the hippy days.
The amount of literature on The Knowledge Argument is staggering, and there are many ways out of the apparent paradox. Frank Jackson who came up with the Knowledge Argument was using it to argue that mental states do not supervene on physical ones. I.e., one's mental states are not uniquely determined in the space of all possible worlds by one's physical state. (He later changed his mind about this, however, and is no longer a dualist.)
One way out of dualism is, as you hinted at, is to maintain that even if dualism is false, there are things that you can't know without having a certain concept in your head, and the only way to get the concept in your head is to have a certain experience which puts your mind into a state that you could not get to via pondering alone.
Another way out of dualism is to deny that Mary acquired any new knowledge when she sees the ripe tomato.
Etc, etc. And the philosophers will probably be arguing about Mary for the next thousand years.
All this tells us is that we have trouble transferring conclusions from the rational bits of brain to the emotional bits. That no amount of secondhand experience will truly prepare you to experience itself doesn't mean there's something special about perception, just that the brain doesn't have any other way to take in what it perceives as the subjective experience.
