... Later Christians would take these brief comments of Paul and develop them according to their own understandings of psychology and the world. Augustine in particular (354-430) developed Paul's thoughts into a highly developed system. For example, Augustine read Paul to teach the total depravity of humanity, the idea that human beings cannot do anything good at all in their own power. Paul never makes such an absolute statement, so if Augustine was right, it would be a God-inspired development of Christian understanding. The Western church would follow Augustine's lead, but the Eastern church to this day comes closer to Paul's understanding.
Paul told the Romans that all had sinned, by which he meant both Jew and Gentile, and he also seems to imply that every individual has sinned as well (e.g., Rom. 3:19). He also told the Romans that the world was under the power of Sin, a power that made it impossible for us mortals in our default condition not to sin (e.g., 7:19). But Augustine lifted statements like these out of a specific argument Paul was making with a specific audience and even then made them to say more than they actually said.
When Paul said that no good dwelt in his flesh (8:18), he also spoke of having a will to do good (8:19), which means he believed there could be good in your spirit.  He said that the power of Sin in us made us "utterly sinful" (7:13), but Paul was talking about how many sin acts the power of Sin causes in a person, not about whether any good is left in you at all. Even Paul's pastiche of quotes in Romans 3:10-18 is poetic, meant to paint a picture of the sinfulness of humanity. None of these verses from the Old Testament originally meant even that every person had sinned, let alone that no good at all existed in humanity.
In short, you will not find in Paul any statement to the effect that God has left no good in humanity at all. It was Augustine who took Paul's teaching just one step further, with Calvin and Wesley following. Perhaps they were inspired to read Paul this way. But the Eastern church is a little closer to Paul in its sense of the thoroughness of human sinfulness, stopping short of absolute statements about whether there might be any goodness in humanity at all.
 Paul's thinking here is thus quite different from Augustine, Calvin, and Wesley, who understood depravity precisely to mean that no one was able to want to do good in their own power...