The notion that happiness comes from a knowledge of things as they really are is wrong. Happiness resides in opinion.
Human affairs are so obscure and various that nothing can be clearly known.
This was the sound conclusion of the Academics, who were the least surly of the philosophers. At least if something can be truly known, it is rarely anything that adds to the pleasure of life. Anyway, man's mind is much more taken with appearances than with reality. This can be easily and surely tested by going to church. When anything serious is being said, the congregation dozes or squirms.