Subject written about by Discipline writer Alain De Botton (10)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
philosophy
(Other definitions for philosophy that I've seen before include "Study of the nature of knowledge and reality" , "pursuit of knowledge" , "Pursuit of truth and understanding" , "Set of principles derived from deep thought?" , "First P of PPE" .)