"It's not publicly observable" -- So? It's still observable by at least 1 observer who can still approach the observations with the scientific method. And who's to say it will stay that way forever? Maybe neuralink and similar tech will give people direct access to each other's subjective experiences, or maybe even cross-species, or trans-human.<br><br>Btw, it is both qualitative (qualia) and quantitative. You can quantify how much pain you feel, what temperature, etc.