The Cogito (n.) is a kind of methodological doubt whereby descartes doubted everything that could possibly be doubted. The only thing that he could not doubted was 'I am doubting' which is to say 'I am thinking'.
The Cogito (n.) is much like the immovable point which archimedes used to demand to shift the entire earth, descartes' attempt at one thing, however slight, that is certain and unshakable.
The Cogito (n.) is the idea that even if a supreme power is deceiving me -then he is still deceiving 'me' I can never be nothing.
Cogito (n.) (phr.) is necessarily true each time I say it or think it — and only then.
The Cogito (n.) is a sentence whose truth is the act of saying it: it states nothing but that act, so it proves itself by functioning.
The Cogito (n.) is a loop in which truth and reality build each other: the proposition is a real truth, and the act of thinking it a true reality.
The Cogito (n.) "I am, I exist" is necessarily true each time I say it or think it — and only then.