 Torin Alter (2013) responds to these arguments by focusing on the distinction between deferential and non-deferential concept possession (the latter is conceptual mastery). He suggests that it is mastery of phenomenal concepts rather than mere deferential possession which matters for the knowledge argument: “Mary makes epistemic progress when she leaves the room because she comes to master or non-deferentially possess phenomenal colour concepts” (2013, 486). And defenders of the knowledge argument can claim that mastery of a phenomenal concept requires actually having experiences with the relevant phenomenal character.