This is popularly translated "I think therefore I am", however some philosophers think that's an oversimplification. Their nitpick rests on the fact that it is unreasonable for Descartes to conclude the existence of the entity having the properties of Rene Descartes based just on thought. Instead, they suggest two more faithful translations (in order of unorthodoxy; followed by an expanded translation):
- I think, therefore am
- "There is a set1 of thoughts, this set must adhere to some entity, I'll call this entity "I"."
- Thought therefore existence
- "There exists an x such that x is a thought, therefore there exists an x2."
It should be noted that both these interpretations can fit into a wider range of metaphysics than the popular translation. In particular, neither of them lead to the concept of a soul as strongly. Materialism, Spinoza's monism, and Berkeley's idealism (to name a few) should find this argument useful.
1: We're assuming it's not an empty set, but it could have only one member.
2: According to some formal logicians, this should be added: "...such that x is identical with x".