Full Idea
In the past one said 'I' is the condition, 'think' is the predicate and conditioned - thinking is an activity which the subject causes; but maybe the reverse is true - and 'I' is only a synthesis produced by thinking.
Gist of Idea
Maybe 'I' am not the thinker, but something produced by thought
Source
comment on René Descartes (Meditations [1641], §2.26) by Friedrich Nietzsche - Beyond Good and Evil §54
Book Reference
Nietzsche,Friedrich: 'Beyond Good and Evil', ed/tr. Hollingdale,R.J. [Penguin 1973], p.62