The Bible.
Because when I was young and I tried reading it I realized that even though millions and millions of perfectly functioning adults believe in something, it might be absolutely wrong or based on basically nothing.
As one human race, we can all come together, try very hard, regardless of class or race or creed or sex, in earnest support of one another, and can collectively make terrible decisions like Daylight Savings Time.
With proper attribution, I think this statement would be worthy of framing and public display. Keep that in mind in case you get famous :)
Even as a confident Christian, there are many people who profess to be Christians but who have a very different understanding of what that means than I.
To me, being a Christian is about having faith in Christ's divinity and the truthfulness of His message, and striving to live my life as is asked of me. I often fail, but I persist.
To others this seemingly cannot be the case, because they attribute words, actions, and attitudes to Christ and to God that serve only themselves and are at odds with scripture.