I think%2C therefore I am' The crossword solutions for the term COGITO-SUM LINK are ERGO, which is a Latin phrase meaning 'I think, therefore I am'. This phrase was famously used by the French philosopher Rene Descartes in his Discourse on the Method, and has since become a popular philosophical concept. It is used to express the idea that one's existence is based on the fact that one can think, and is often used to express the idea of self-awareness.