The term 'I Think, Therefore I Am' is famously attributed to the French philosopher Rene Descartes. The crossword solution for the term 'THINKER' is Descartes, which has nine letters. Descartes is widely regarded as one of the most influential figures in the history of philosophy and is credited with laying the foundations of modern Western philosophy. He is best known for his philosophical statement 'I Think, Therefore I Am, ' which is a foundational principle of his philosophy.