Descartes claims that his existence of a thinking thing is the one certain truth, which can serve as the foundation for all other knowledge.

Descartes claims that his existence of a thinking thing is the one certain truth, which can serve as the foundation for all other knowledge. With nothing more than just the knowledge that he is a thinking thing, Descartes goes on to further meditate on more monumental topics. Not only does this realization of his existence serve as the foundation for all other knowledge, it served as the starting point of a new era of modern …

…most important. For Descartes the existence of a thinking thing was the only certain truth that he was aware of and became the foundation for all other knowledge. In knowing that he was a thinking thing he was able to find one thing that couldn't be doubted. This took him one step closer to finding greater and more purposeful knowledge and gave him a systematic process to refer to in the certainty of other discoveries.