Statements of belief seem to be about reality outside of yourself but are actually about you.

For example: I believe that Abraham Lincoln was a good President of the U.S. This sentence seems to be about Lincoln but it is really about the 'I' who said it. After all, Lincoln could have been lousy as President and I might still believe that he was good.

The reader is interested in WHY you believe a claim and not, usually, that you believe it.