How would you show what is true, without believing?
I can't. Nobody can. Neither can you. Everyone is either putting their trust in God says is Truth, or in what man says he thinks/believes is true. Man can be individual - your own personal "beliefs", or corporate. God's Truth is never changing and has always been. Man's "truths" are extremetly varied and are as changing as the shifting sand. We all lean on one or the other (God or man) as the support for our beliefs. It is impossible to "show what is true" to someone who is leaning and trusting on what you are not. It just can't be done. Apples and oranges. There is only one way that one can truly change their support. And that is by the grace of our God - Christ Jesus. Any other way is just not a way at all.