Do you mean this in the sense that all perceptual experiences seem somehow unsatisfying when quantified? That is, we can study the sensors, we have some ideas about how the signals from those sensors are post-processed in the brain, we can do experiments to determine what things people can (or do) differentiate or detect, and we can observe that have enough of a shared experience of the experience to be able to discuss and use the concepts in practical situations. However, for all that, somehow we have the feeling that we're not able to describe the "real thing".
