In the glossary of the book, “The Christian Faith – A Systematic Theology For Pilgrims On The Way” Michael Horton defines Total depravity: theological position that every aspect of human nature has been corrupted by the fall – body, soul, mind, heart, and will.
Earlier in his book, Chapter 13, Horton states, “Everyone has the natural ability to render God faithful obedience, but after the fall, ‘we are sold [into slavery] under sin’ (Ro 7:14), our moral ability held captive not to a foreign army but to our own selfishness, idolatry, greed, and deceit. ‘None is righteous, no, not one; no one understands, no one seeks God’ (Ro 3:10-11). This is not simply hyperbole: even when we pretend to be seeking God, we are in fact running from the God who is actually there. If the self-help sections of the average bookstore are any indication, we are, like Paul’s Athenian audience, ‘in every way …. very religious’ (Ac 17:22). But God is not worshiped; he is used. ‘Spirituality’ no less than atheism suppresses the specificity of the God revealed in Scripture.
The fact that we are still God’s image-bearers and consequently possess all of the requisite natural ability for relating to God and other in covenant faithfulness – and the fact that this is even realized in our sense of duty to the rule of law – renders us culpable (Ro 1:18-2:16). The fault lies not in that we cannot but that we will not turn from our sin to the living God (Jn 8:44). Captive to sin, ‘in Adam,’ we are nevertheless willing accomplices to our own imprisonment (Ro 5:12). Only when God seizes us and liberates our captivity are we truly free to be the human beings that we are (Jn 8:36).
Total depravity therefore means not that we are incapable of any justice or good before our fellow humans (civil righteousness), but that there is no Archimedean point within us that is left unfallen, from which we might begin to bargain or to restore our condition (righteousness before God).”
Michael Horton, The Christian Faith – A Systematic Theology for Pilgrims On the Way, Zondervan, 2011, Pgs. 433-434, 1002