Often regarded as the first "modern" thinker for providing a philosophical framework for the [natural sciences]? as these began to develop. In his "Meditationes" Descartes attempts to arrive at the principles of knowledge by first rejecting everything he knows, or thinks he knows, about the world. Starting thus from scratch, he discovers that the only certainty he has left is that he himself exists: the famous cogito ergo sum, often rendered as "I think, therefore I am". From this first principle he proceeds to construct a system of knowledge, discarding perception? as unreliable and instead admitting only deduction as a method. Halfway through the "Meditationes" he also claims to prove the existence of a benevolent God, who, being benevolent, has provided him with a working mind and [sensory system]?, and who cannot desire to deceive him, and thus, finally, he establishes the possibility of acquiring knowledge about the world based on deduction and perception.