How did Descartes use clear and distinct ideas as a criterion of truth?

René Descartes utilized "clear and distinct" ideas as a criterion of truth to overcome the skepticism he encountered through his methodic doubt. After establishing his own existence through the cogito, ergo sum intuition, he argued that any idea perceived with the same clarity and distinctness must also be true.12

Descartes reasoned that because God is perfect and not a deceiver, God would not allow him to be mistaken about perceptions that are clear and distinct. By proving the existence of God, Descartes aimed to provide a metaphysical foundation for knowledge beyond his own existence, asserting that clear and distinct ideas serve as a reliable guide to reality.312

However, this approach is famously challenged by the Cartesian circle. Critics, such as Antoine Arnauld, pointed out that Descartes’s reliance on clear and distinct ideas to prove God’s existence—while simultaneously using God’s existence to guarantee the truth of those clear and distinct ideas—constitutes circular reasoning. Consequently, the validity of his criterion remains a central point of debate in philosophy.321