Now the fourth post in the third section of theology in bullet points.
1. The apostle Paul put it this way, "There is no one righteous, not even one... there is no one who seeks God" (Rom. 3:10-11). He was paraphrasing Psalm 14, which probably was much more limited in scope originally, but Paul applies it toward a doctrine of all humanity's default sinfulness.  "All have sinned and are lacking the glory of God" (Rom. 3:23) 
Augustine (354-430) took Paul's comments here and constructed a doctrine of total depravity. The idea of total depravity is that, in its current fallen state, humanity is not able to do any good whatsoever in its own power. He formulated this idea while combatting the Pelagians, who believed that humanity was not totally fallen morally and could still do good in its own power. 
John Calvin (1509-64) especially would then pass on Augustine's interpretation in the Reformation to say that, because we cannot choose God at all in our own power, then those who are saved must do so entirely because God has chosen us (election) and empowered us (irresistable grace). This is the idea of predestination, that only those God has specifically chosen can be saved for eternity. The rest will inevitably go to hell because they have no power to do good in themselves and God has not chosen them.
John Wesley (1703-91) also believed in total depravity, but he believed that the Holy Spirit, at some point in a person's life, empowered you to move ever so slightly toward God if you would so choose. If you did, then the grace would increase and it would eventually lead to eternal salvation in heaven rather than eternal damnation in hell. In this way, while Wesley believed we could do no power whatsoever on our own, he believed God's power made our "election" conditional on our responses to God.
Strictly speaking, Augustine may have over-read and overly systematized Paul himself. Paul really only seems to be arguing for a thorough depravity of humanity. In that sense, Eastern Orthodoxy may come closer to Paul than Western Christianity. Paul claims that 1) every human has sinned and that 2) no one is righteous in his or her default state.  But Paul does not say, "No one can do a single good thing in his or her own power."
Nevertheless, sometimes it is hard to look around at the world and not find yourself repeating the words of Paul and the psalmist. Is there anyone who is righteous out there? Does not everyone simply do what is to their own advantage whether it hurts other people or not? Who sacrifices their own pleasure for the sake of a greater good? Who gives to those in need the extra they have? Who does not cling violently to what they think is "theirs"--my money, my rights, what I deserve? Who does not lie when it is to their own advantage? Who does not try to manipulate others to get what they want? Who listens to the other without insisting that their way of thinking and doing is the only right way?
2. This situation of humanity leads us to the question--why? Why is humanity bent toward hate of neighbor and usurping God's place? In the first post of this section on evil, we suggested that the two absolute commandments of Christianity--love God and love neighbor--provided the two basic categories of sin. You can sin by defying God's authority and you can sin by wronging others.
When we say that humanity is "bent to sinning," we are saying that the default state of humanity is to usurp God's authority and to wrong others. Both of these imply that the central feature of sin is the human bent toward itself. At the heart of sin is the human tendency to take for itself what is rightfully God's and to take for itself in a way that takes away from others.
Why is this the case? For Augustine, the fundamental cause was a "sin nature" we have inside us. When Adam sinned, we lost the moral image of God entirely. Human nature became thoroughly corrupted. Our individual acts of sin thus result from our sin nature, a nature that all humans now have because of Adam's original sin.
Augustine had a very specific interpretation of Romans 5:12. He did not know Greek, but his sense of the Latin translation was that this verse indicated that all humanity had sinned "in" Adam. He understood the verse to say that, "And thus death passed into all humans, in whom all sinned." We all thus needed infant baptism to atone for our participation in that original sin.
Almost all translations today recognize that Paul was rather saying that death passed to all humans because we all sin like Adam. Paul was thus not saying that humanity stands under God's condemnation for Adam's sin but because we all sin like Adam did. As Ezekiel 18:4 says, "The one who sins is the one who will die." God does not hold us as individuals responsible for the sins of others, including the sin of Adam.
So how did Paul understand Adam's sin to have impacted us? He understood the world to have come under the power of Sin as a result of Adam's sin. Despite the way some versions used to translate the word, Paul did not use the term "sinful nature" to refer to the power of Sin over me. Rather, the word he uses is "flesh," that is, my skin.
Flesh, for Paul, is not intrinsically evil. It is, rather, "weak" (Mark 14:38). It is susceptible to the power of Sin. Before Adam's sin, Sin did not reign as a power in the world. After Adam's sin, the world now stands under the power of Sin. Without the power of the Spirit to counteract the power of Sin, humanity is helpless to do the good, even if we should want to do so (e.g., Rom. 7:15). .
Paul can thus use the word "flesh" in more than one way. He can use it to refer merely to my human "skin" as weak but not necessarily sinful (2 Cor. 12:9). It is probably significant that Paul does not attribute the inherent weakness of human skin to Adam. What Paul attributes to Adam is the power of Sin over our skin. Paul can thus use the word "flesh" to refer to that aspect of humanity's current state that is subject to sin and say that, "those who are in the flesh cannot please God" (Rom. 8:8).
The current bent of humanity is toward evil. It is bent to seek itself over God and itself over others. Historically, Christians have believed that the sin of Adam brought the world and human flesh under the power of Sin. The result is that we cannot do the good in our own power, indeed, that no one even will want to do the good apart from the power of the Spirit.
Further, Christians believe that a parallel Fall took place in heaven with Satan and his angels. Adam's fall may have made the world susceptible to the power of Sin in some impersonal way. Satan's sin brought personal powers of sin into play in the world. We not only have the impersonal force of Sin over us. We face the personal faces of evil and temptation in those beings who chose against God. 
Whatever the cause, Christians believe that the bent of humanity at this time is toward evil, and we cannot do good apart from the power of God.
Next week, E5: All have sinned.
 Psalm 14 is poetry, and this speaks somewhat hyperbolically of the state of things in the psalmist's own day (he was not making a statement about humanity for all time). In particular, he is speaking of the fool who would say in his or her heart that God was not around (Ps. 14:1). As an example, the psalmist surely is not including himself among such fools. "Not even one" is thus quite likely hyperbole.
We should not consider it a problem that New Testament authors heard different truths in the words of the Old Testament than were exactly what those words likely meant originally. This flexibility of language is the primary tool the Spirit uses to speak so directly to so many different people.
 Author's translation.
 These ideas were condemned at a regional council at Carthage in 418 and ratified at the universal Council of Ephesus in 431.
 Even here, although Paul did seem to believe that every human (except for Christ) has sinned, that is not really his point in Romans 3:23. In Romans 3:23, Paul's point is that all have sinned whether you are a Jew or a non-Jew. Both have sinned and thus need Christ. "All," both non-Jew and Jew, have sinned.
 You might note that, contrary to Augustine, the default problem in Romans 7 is not that humanity does not want to do the good, as if we are totally depraved. The problem is that, even when we want to do the good, we do not have the power to do it.
 The impact of evolution on this discussion would be profound in that it potentially questions the idea of a Fall. On the one hand, one might suggest that the drive toward the self is part of God's creation but that the power of Sin introduced with Adam seriously warped that drive. If one only takes Adam as a metaphor, then one would have to conclude that God created us with conflicting drives, one of which pushes us toward self-interest and the other of which calls us toward others. The default human state would thus be one of continual conflict.