Full Idea
The essential indexical is a problem for the view that belief is a relation between subjects and propositions conceived as bearers of truth and falsity.
Clarification
'Indexicals' are words like 'I' and 'now', where meaning partly depends on context
Gist of Idea
Indexicals are a problem for beliefs being just subject-proposition relations
Source
John Perry (The Problem of the Essential Indexical [1979], 'Intro')
Book Reference
'Self-Knowledge', ed/tr. Cassam,Quassim [OUP 1994], p.167
A Reaction
My immediate reaction would be that it depends on how you conceive of 'propositions'. If they are objective, you have a problem. I take them to be subjective events in brains, and the indexical meaning to be evident within the proposition.