Taking knowledge as a starting point › The Problem of Always Recognizing Your Own State

The book's anti-luminosity argument concerns an apparently secure kind of access to one's own mind. A condition is luminous if, whenever it obtains, the person is in a position to know that it obtains. Being in a position to know differs from actually knowing: someone might never have considered the question. The issue is whether attention could always remove the ignorance. See chapter 4, sections 4.1–4.3.

Williamson asks us to imagine feeling cold at dawn, gradually warming up, and no longer feeling cold by noon. Throughout the process the person carefully attends to how they feel. The changes are so slow that successive moments differ too little for the person to discriminate reliably. Feeling cold seems a promising candidate for luminosity: surely, whenever you feel cold, you could recognize that you do.

The argument adds a reliability requirement. In this carefully described process, knowing that you feel cold at one moment requires enough margin for error that you still feel cold at the next, extremely similar moment. Otherwise almost unchanged confidence would be mistaken immediately nearby. If feeling cold always put the attentive person in a position to know it, feeling cold at one stage would yield knowledge at that stage, and the margin requirement would carry feeling cold into the next stage.

Repeat that reasoning and it carries feeling cold all the way to noon, contradicting the stipulated endpoint. Williamson rejects the luminosity assumption. This is a reconstruction of his argument, not an empirical finding about a measured temperature threshold. Its force depends on the margin premise as well as the described continuity of the process. Rejecting that premise is a substantive way to resist the conclusion; declaring introspection obviously transparent simply restates what the argument challenges.