“Descartes engaged in a very interesting teaching procedure, and one from which he himself learned a great deal. He began with doubting the existence of everything except himself. He insisted that his own existence was not open to doubt and rebuilt his entire thought system on the one premise, ‘I think, therefore I am.’ It is noteworthy that he arrived at accepting the entire system he originally doubted, solely on the basis of this one piece of knowledge. There was, however, a distinct shift in his own perception. He no longer questioned the reality of what he perceived, because he knew he was there.” (ACIM, COA ed., T-3.XI.11:1-6)
This piece about Descartes is new to the complete edition of A Course in Miracles. On one piece of knowledge, Descartes based his whole system of thought. He believed, basically, that he existed. This is even more fundamental than the aspect of thinking that is a part of his great revelation. “He knew he was there.”
We also know that we are here. We can extrapolate this understanding to greater knowledge if we realize that just one piece of information can set us free. This piece will differ from person to person, because our pasts are different, and so the healing of the unconscious that needs to happen will also differ. But when you come upon a piece of knowledge—and it will be knowledge—that is unassailable, then we must hang our hat on that. It will be enough.
Pray for the gleaning upon the mind of that piece of knowledge that will save. And then go out and teach it. Others will learn from our own revelation.