Meaning of cogito, ergo sum*

co•gi•to er•go sum

Pronunciation: (kō'gi-tō" er'gō soom' Eng. koj'i-tō" ûr'gō sum', er'gō), [key]
— Latin. Latin.
  1. I think, therefore I am (stated by Descartes as the first principle in resolving universal doubt).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.