Cogito ergo sum
Cogito ergo sum, Latin for 'I think, therefore I am,' is the point Descartes reaches in his Meditations after doubting everything he possibly can, including the reliability of his senses and the existence of the external world. He finds that the act of doubting itself proves there is a thinking thing doing the doubting. Whatever else might be false, the fact that he is thinking, and therefore exists, cannot be doubted while he is doubting it.
Why it matters
It gives Descartes one certain fact to rebuild knowledge from, and it makes the thinking self, rather than God or tradition, the starting point of modern philosophy.
Also written: cogito
Where it comes up
Read about Cogito ergo sum on Wikipedia
Sources
- René Descartes Stanford Encyclopedia of Philosophy
- Descartes Internet Encyclopedia of Philosophy
