Are you certain?
Kyle Amon,  Page 7 

Certain
adj. 1. Definite; fixed. 2. Sure to come or happen; inevitable. 3. Established beyond doubt or question; indisputable. 4. Capable of being relied on; dependable. 5. Having or showing confidence; assured. 6.a Not specified or identified but assumed to be known. b. Named but not known or previously mentioned. 7. Perceptible; noticeable. 8. Not great; calculable.

Usage Note: Although certain appears to be an absolute term, it is frequently qualified by adverbs, as in fairly certain. In an earlier survey a majority of the Usage panel accepted the construction Nothing could be more certain.