Abstract
René Descartes initiated the modern era by his methodical attitude based on doubting about everything (de omnibus dubitandum est) while unless anything is not clear (clare et distincte) it cannot be considered true. This thinking failed because the author was not in his method consistent enough.
He identified truth and certainty in spite of its contradiction. Relation to truth destroys any certainty and certainty on the other hand impedes the rout to truth.
Truth lays bare in a question and not in a statement. One of the consequences is necessity to swap the still scholastic notion of truth as a correspondence (adaequatio) between a thought and reality with the notion defining reality by truth.
This step requires a "kopernikian" turn from the philosophy of "I know" to the philosophy of "I am". This switch will not be easy.