Wolfgang, when I say something is my opinion, I am making a statement about me, not about the world. Obviously I can be wrong, we all can be wrong.

I could end every sentence where I say what I think to to be true or probable with the words "but of course I could be wrong." But I generally don't think it's necessary - those words are always there implicitly. Anyone who doesn't always carry those words inside them "of course I could be wrong" is probably barking mad.

And true enough, when I say "I cannot imagine" I am using a figure of speech, meaning "I do not believe that this is probable". Strictly speaking I can imagine all kinds of things that I do not think are probable.