Positiveness.
That which is sure; reality; a photograph having the lights and shade of the real object.
Positively.
Bonaparte knew well what he wanted, but he did not like to name it in any positive way. – The Project Gutenberg Memoirs of Napoleon Bonaparte by Bourrienne, Constant, and Stewarton
I wish, my dear, you would be less positive. – When Ghost Meets Ghost by William Frend De Morgan