Early Modern Philosophy
What did Descartes mean by “clear and distinct ideas”?
Descartes thought that there was a “natural light” of reason by which one could be sure of one’s thoughts. Descartes wrote in his Principles of Philosophy (1644):
I term that “clear” which is present and apparent to an attentive mind, in the same way that we see objects clearly when, being present to the regarding eye, they operate upon it with sufficient strength. But the “distinct” is that which is so precise and different from all other objects that it contains within itself nothing but what is clear.”
In other words, the thinker has an intuitive or direct experience of clarity and about what he or she is clear about. Descartes was relying on our ability to recognize when we know something for sure in all its detail.