Full Idea
[The Cogito] means positing our belief in the concept of substance as 'true a priori': that if thinking occurs there must be something 'that thinks' is, however, simply a formulation of our grammatical convention that assigns a doer to each deed.
Gist of Idea
The Cogito means assuming substances, and a grammatical convention assigning doers to deeds
Source
Friedrich Nietzsche (Fragments from 1886-87 (v 17) [1887], 10[158])
A Reaction
He says the Cogito is not a certainty, but just 'an intensely strong belief'. The idea that it is just a linguistic convention anticipates a common twentieth century criticism.
Book Reference
Nietzsche,Friedrich: 'Fragments from 1886-87 (v 17)', ed/tr. Leiner, George H. [Stanford 2025], p.315
Related Idea
Idea 6619 Perhaps 'I' no more refers than the 'it' in 'it is raining' [Lowe]