I Think Therefore I Am

"Cogito, ergo sum" is the foundational proposition of René Descartes's philosophy, first published in French as "Je pense, donc je suis" in the Discourse on the Method (1637) and restated in Latin in the Meditations on First Philosophy (1641). Having subjected all his beliefs to radical doubt, Descartes found one thing that could not be doubted: the very act of doubting proved that a thinking subject existed. From this indubitable starting point he attempted to rebuild the entire edifice of knowledge. Gottfried Wilhelm Leibniz and later Immanuel Kant both offered influential criticisms of the argument.