I have looked at no less than 10 online definition sites and in my own personal dictionary and have not seen even one that comes close to what you think conviction means. There is nothing in the definition of conviction about unshakable faith or lack of evidence. In fact, in legal terminology, the term convicted is used when a person who is accused of a crime is found guilty of that crime by a judge, jury or court based on evidence presented.

In short, don't piss down my leg and call it rain.