Full Idea
It is possible that those who think that '2 and 2 make 4' is the content of my representations may be forced to resort to a transcendental and subjective principle of unification - in other words, the I.
Gist of Idea
If you think of '2+2=4' as the content of thought, the self must be united transcendentally
Source
Jean-Paul Sartre (Transcendence of the Ego [1937], I (A))
Book Reference
Sartre,Jean-Paul: 'The Transcendence of the Ego' [Routledge 2004], p.6
A Reaction
He suggests that thoughts themselves unite the mind, externally. If you think of thoughts as internal, you must resort to a transcendental fiction to unify the mind. Personally I think the mind is inherently unified by brain structures.