Full Idea
If I leave a trail of sugar, and realise 'that I am making a mess', ...when we replace the word 'I' with other designations of me, we no longer have an explanation of my behaviour, or an attribution of the same belief, so it is an 'essential indexical'.
Gist of Idea
If we replace 'I' in sentences about me, they are different beliefs and explanations of behaviour
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
[compressed] A famous observation of Perry's, which leads him to challenge traditional accounts of belief and of propositions. I don't think I see a problem, if we have a thoroughly non-linguistic account of essentially unambiguous propositions.