"To know is to doubt.” Is this a paradox we have to live with?

Since this is the philosophy section, I would take as an example Descartes' formula "I think therefore I am", which he introduces in his Discourse on Method after a meditation in which he discovers that his thought is based on doubt. Doubt is the greatest introduction to thinking, and therefore to being. Doubting is human, and doubting leads us, as you said, to question everything, and to be able to have an abstract reflection on things, even in everyday life.