Full Idea
The proposition expressed by 'Cicero is an orator' represents things as being exactly the same way as does the proposition expressed by 'Tully is an orator'. Hence two sentences express the same proposition. Fregeans about names deny this.
Clarification
Cicero and Tully are the same person
Gist of Idea
'Cicero is an orator' represents the same situation as 'Tully is an orator', so they are one proposition
Source
Trenton Merricks (Propositions [2015], 2.II)
Book Reference
Merricks,Trenton: 'Propositions' [OUP 2015], p.41
A Reaction
Merricks makes the situation in the world fix the contents of the proposition. I don't agree. I would expand the first proposition as 'The person I know as 'Cicero' was an orator', but I might never have heard of 'Tully'.
Related Idea
Idea 9453 Sentences saying the same with the same rigid designators may still express different propositions [Bealer]