What Christian doctrine can we prove?

G.K. Chesterton, the British novelist, once said that human depravity is the one Christian doctrine that can be proved. One would think so. Evidence of sin is everywhere. You see crime, violence, wars, fraud, pornography, and all sorts of evil, and you see it every day. Just watch TV. Even the denial of sin from unbelieving men and women is itself an evidence of the human tragedy. What is the antidote? I believe the antidote is Christ, and so does Lancelot Andrewes who lived from 1555 to 1626. Here is an excerpt from his Confession:

Confession

Lord,

as we add day to day

so sin to sin.

The just falleth seven times a day;

and I, an exceeding sinner,

seventy times seven;

wonderful, a horrible thing, O Lord.

But turn with groans

from my evil ways,

and I return into my heart,

and with all my heart I turn to Thee.