The second chapter of Mark Biddle’s book, Missing the Mark, discusses sin from a very important angle: sin as the desire to be more than human. He’s not keen on making this simply hubris or pride or arrogance, but the inconquerable desire for humans to live within their limits and the attempt to be more than they are.
He begins by looking at passages in the Bible that deal with the classical issue of apostasy, and he does so in terms of violating the covenant — OT texts, the sin unto death in 1 John 5 and “apostasy” in Hebrews. He’s good here; balanced and fair.

The rest of this chp deals wtih the Bible on Arrogance: O! To be more than human. Deftly, he begins with Ecclesiastes and the desire on our part to fail to recognize that we are creatures, that we are less than God, that in spite of having ‘lm (olam) in our hearts, absolute knowledge is found only in God. [Note to self: emerging thinkers ought to deal with Job and Ecclesiastes more often.]
Then he has a thoughtful section on Paul: he finds “original sin” to be “sinning on the part of all humans” rather than somehing inherited; sin is universal. “One is a sinner, not because Adam’s sin automatically made one so, but because one actively participates in Adam” (38). Not only this, but “all” means universal in the true sense: each person violates relationship with God by striving to be more than God made them to be. Reaching for too much,etc..
Fundamentally, sin is the failure of relationship with God by not being what we are meant to be: authentic humans, Eikons, not God.
Here’s something I thought of:
Liberalism’s essential sin, if I read Biddle aright, is the belief in the perfectibility of humans and society (striving for utopia without facing the reality of sin).
Fundamentalism’s sin is the refusal to be authentically human (sinful while thinking they are the utopia).
Needs some polishing, but you might explore these two lines of thinking with me.