Actually, while opinion and theory are seperate, you are still not completely correct. All you need is something that hints at a possibility to have a theory. A hypothesis doesn't even require that much. Once you gather enough evidence to prove said theory, then it becomes fact. Evidence and proof are not completely the same thing.

Opinion, requires no proof or even any logic. I can say that cheese tastes like dog[img]/xxx.gif[/img][img]/xxx.gif[/img][img]/xxx.gif[/img][img]/xxx.gif[/img]. I will never have to taste dog[img]/xxx.gif[/img][img]/xxx.gif[/img][img]/xxx.gif[/img][img]/xxx.gif[/img] to hold this opinion. Hell, i can eat dog[img]/xxx.gif[/img][img]/xxx.gif[/img][img]/xxx.gif[/img][img]/xxx.gif[/img] and know for a fact that I'm wrong and still hold that opinion.