…a lady of what is commonly called an uncertain temper --a phrase which being interpreted signifies a temper tolerably certain to make everybody more or less uncomfortable.
Everyone who observes himself doubting observes a truth, and about that which he observes he is certain; therefore he is certain about a truth. Everyone therefore who doubts whether truth exists has in himself a truth on which not to doubt.... Hence one who can doubt at all ought not to doubt the existence of truth.