Stephanie asked:

Explain the cogito?

============

The Cogito is Descartes famous argument to prove his own existence. Its most famous formulation is
"I think, therefore, I exist" (although that formulation appears in only one place in Descartes' works).

The idea behind it is that it is self-refuting to doubt (or deny) that one exists because no one can
doubt or deny that one exists unless he already exists. (Of course, as Descartes himself recognized,
that shows only that you must exist while you deny or doubt that you do, not that you must exist when
you do not.)

Ken Stern