Full Idea
We arrive at the concept of suicide by considering both occurrences in the sentence 'Cato killed Cato' of the proper name 'Cato' as simultaneously replaceable by another name, say 'Brutus', and so apprehending the pattern common to both sentences.
Gist of Idea
We arrive at the concept 'suicide' by comparing 'Cato killed Cato' with 'Brutus killed Brutus'
Source
Michael Dummett (Frege philosophy of mathematics [1991], Ch.14)
Book Reference
Dummett,Michael: 'Frege: philosophy of mathematics' [Duckworth 1991], p.173
A Reaction
This is intended to illustrate Frege's 'logical abstraction' technique, as opposed to wicked psychological abstraction. The concept of suicide is the pattern 'x killed x'. This is a crucial example if we are to understand abstraction...