If Jesus saved us by doing something in us by the Holy Spirit, then there would not have been a need for the incarnation. Jesus could have stayed in heaven and could have sent the Holy Spirit into the world to transform people into his likeness. No life, death and resurrection of Jesus needed. Of course, that would never work because we are not saved by being like Jesus, although many believe that we are.
Jesus saves us, not by doing something in us, but by doing something that is totally and completely outside of us. Paul wrote, "But God commended his love towards us, in that while we were yet sinners, Christ died for us" Romans 5:8. Our salvation took place over 2,000 years ago before we were born. How does Jesus save us? Jesus saves us by fulfilling all of the demands of God's law. Jesus saves us by atoning for our sins. All that Jesus is, and all that Jesus did, was for our justification and our salvation.
This is why we are saved and justified by faith alone. The work of salvation has ALREADY been done. Before Jesus died on the cross, he said, "It's finished" what he meant by that is that salvation had been provided for everyone, Hebrews 2:9. No one needs to be predestinated, no one needs to be holy. Salvation has been provided for all that do nothing more than call upon his name, Romans 10:13.
But many will say, no, we must be baptized, and others will say, we must keep the commandments, and then the Calvinist will say you must be predestinated. The "We musters" appear to be endless. All that is required of us is that we believe in Jesus, we believe that Jesus fulfilled the law for us, we believe that Jesus atoned for our sins. That's it. Nothing more is required. Salvation is by faith alone, because it is by Christ alone.