God's choice of certain individuals unto salvation, before the foundation of the world, rested soley on His own Sovereign Will.
His choice of particular sinners was not based on any foreseen response or obedience on their part, such as faith, repentance, etc. On the contrary, God gives faith and repentance to each individual whom He selected. These acts are the result, not the cause, of God's choice.
Election therefore was not determined by or conditioned upon an virtuous quality or act foreseen in man. Those whom God sovereignly elected He brings through the power of the Spirit to a willing acceptance of Christ. Thus God's choice of Christ, is the ultimate cause of salvation.
Romans 9:11 ; 11:5,7 ; 11:28 ; 8:38-39
1 Thessalonians 1:4
2 Thessalonians 2:13 ; 14:2
2 Peter 1:10
2 Timothy 1:9,10