My own family convinces me. And if they behave in a particularly holy manner, my church will certainly remind me. I need not consult the world for evidence. When someone first suggests that you are totally depraved, it feels like a kick in the teeth. It hits where it hurts most - right in the pride.
Depravity sounds so ugly and our culture prides itself on appearing beautiful.
We all look so good, and outwardly behave so well. Generally speaking, we like to think, we are a good lot. But the Scriptures undeniably and starkly affirm that we are sinful and that our sin runs deep and wide through our being. We are not as bad as we possibly could be. There is nowhere in our soul some small reservoir of innocence - every part is tainted.