"So why did Paul count all his biological advantages and efforts to be "rubbish"? That's the big question to think about. Protestants erroneously presume the reason why Paul's righteousness was "rubbish" was because his works were tainted by sin. But nothing he mentioned was sinful, and the context nowhere suggests that Paul's sinfulness was the problem, nor can his Jewish racial qualities be considered sinful. So if the real problem here is that Paul is a sinner, then by Protestant logic, Paul has no righteousness at all, and thus Paul should not even be speaking of a "righteousness of my own" and "blameless" in keeping the law. If you think about it, calling your righteousness "dung" is kind of an oxymoron. It's like saying "my sinful good deeds". There's no such thing. So it's nonsense for Paul to be speaking of his own "righteousness" if it's not actually a real righteousness. And if Paul was trying to argue that the Law couldn't save because he himself couldn't keep it, his opponents would laugh at him for such an excuse. Just because Paul cannot keep the law doesn't mean nobody else can. This leaves only one alternative: if Paul did indeed keep the law "flawlessly" and yet this amounted to "rubbish," then this can only mean the law never did save even if kept perfectly. And that's truly what he's getting at."
The Apostle Paul calls his "biological efforts" rubbish, not because they are inherently corrupt, but that all the good things that he did in his days as a Pharisee counted for nothing. All good works in the world cannot save us. Prior to his conversion, Paul would have viewed his faithfulness to the Law as meriting God's favor. Even the righteousness that Adam had prior to his fall would not be adequate to address our problem of sin. Scripture is clear that no one can or does keep the Law (Romans 3:9-23).
If Adam had obeyed God in the Garden of Eden, then he would have been truly righteous before God and given blessings of every sort. But the human race is fallen. Even perfect conformance to the Law cannot cleanse our sinful hearts. Jesus Christ Himself pointed this out to the rich young ruler. The Law cannot save us because it does not offer the forgiveness of sin. It cannot purify our hearts.
"When Paul says he wants to attain the righteousness that comes "through faith in Christ, the righteousness from God," the first thing to note is that nothing here suggests this is "Christ's Righteousness" or that it is "imputed". Protestants can only project/assume this. They cannot actually show this from the plain reading of the text! So much for them caring about what Scripture plainly teaches! Protestants blindly assume that Philippians 3:8-9 is teaching that the "righteousness of the law" needs to be attained by us so that we can be saved, and since we cannot attain it by our own efforts, they say that Jesus must perfectly keep the law in our place and impute this "righteousness of the law" to us, as if we perfectly kept the law ourselves. But notice that the "righteousness of the law" is not the same as what Paul contrasts to "the righteousness that comes from God." These are two different types of righteousness! What is this righteousness from God that Paul eagerly wants to have? This is where things get really embarrassing for the Protestant side."
When Paul says, "not having a righteousness of my own...," he is clearly referring to an external or alien righteousness that we do not possess. When he speaks of righteousness "that comes from the law," he is referring back to his previous statement, "as to the law, a Pharisee...as to righteousness under the law, blameless." He was outwardly blameless and not pure in heart. When he says, "having a righteousness...which comes through faith in Christ, the righteousness from God that depends on faith," Paul is referring to imputed righteousness. He is referring to a righteousness that comes through faith and not our good works.
"The truth is, Paul tells us what he means by attaining this "righteousness from God" in the very next verses, but you will almost never see Protestants even aware of these verses. Look around and ask around and see how often they cite Philippians 3:9 but leave out (often out of total ignorance) verses 3:10-11! Paul gives it to us plainly: "that I may know Jesus and the power of his resurrection, and may share his sufferings, becoming like him in his death, that I may attain the resurrection" Clearly, Paul is saying he wants an inner transformation to happen to him, with his soul experiencing the power of God, causing it to be transformed in the suffering, death, and resurrection of Jesus. There is nothing "imputation" about this, and in fact it directly refutes Imputation and Christ's Righteousness. This theme events fits the earlier verses, such as 3:3 where Paul says Christians have the spiritual circumcision done on them by the Holy Spirit (Rom 2:29). Again, nothing Imputation about that."
Verses 10 and 11 refer not to our justification, but to sanctification and glorification. The Reformation Study Bible notes:
"9–11 Verse 9 speaks of justification, v. 10 of sanctification, and v. 11 of glorification. The sequence of privilege-death-exaltation suggests a connection with 2:6–11."
The Apostle Paul in Philippians 3:10 speaks of the Holy Spirit's work in sanctification. That process is distinct from and has a consequential relationship to our justification. We gradually become more like Christ through the indwelling of the Spirit of God. The imputation of righteousness becomes more evident as we grow in sanctification.