What is "sin" and what does it do?

From Cornelius Plantinga's classic contemporary treatment of the Biblical doctrine of sin:

"The Bible presents sin by way of major concepts, principally lawlessness and faithlessness, expressed in an array of images: sin is missing the target, a wandering from the path, a straying from the fold. Sin is a hard heart and a stiff neck. Sin is blindness and deafness. It is both the overstepping of a line and the failure to reach it -- both transgression and shortcoming. Sin is a beast crouching at the door.

"In sin, people attack or evade or neglect their divine calling. These and other images suggest deviance: even when it is familiar, sin is never normal. Sin is disruption of created harmony and then resistance to divine restoration of that harmony.

"Above all, sin disrupts and resists the vital human relation to God, and it does all this disrupting and resisting in a number of intertwined ways. Sinful life, as Geoffrey Bromiley observes, is a partly depressing, partly ludicrous caricature of genuine human life."

-- "Not the Way It's Supposed to Be" p. 5 (Eerdmans 1995)