Adam was tested by God, failed the test, and sinned. Man is a sinner because of Adam, and from the very time of conception, has a sin nature. Because of this nature man's whole disposition is evil. It remains evil until the Spirit of God changes his heart by applying the blood of Jesus Christ. This gives him the capacity to believe.
Man is like a broken down junkyard car.
It has a cracked engine block and does not run. It has leaked out all its fluid, and has no gas. It has four flat tires and the body is all smashed up. The answer is never. It needs a mechanic, and His name is Jesus.