The elect were chosen by the grace and mercy of God alone

19Thou wilt say then unto me, Why doth he yet find fault? For who hath resisted his will? 20Nay but, O man, who art thou that repliest against God? Shall the thing formed say to him that formed it, Why hast thou made me thus? 21Hath not the potter power over the clay, of the same lump to make one vessel unto honour, and another unto dishonour? 22What if God, willing to shew his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction: 23And that he might make known the riches of his glory on the vessels of mercy, which he had afore prepared unto glory, 24Even us, whom he hath called, not of the Jews only, but also of the Gentiles? - Romans 9


The argument goes something like this that God cannot be merciful to vessels that are unfallen, because mercy presupposes fallenness. But is this true? When one considers the end to which God chose the elect and the non - elect one ought to see that it was God's grace and mercy to save some and to damn others before they had done anything good or wrong.
Ultimately, God could have chosen to save person a rather than person b. But, He did not. Mercy and Grace are undeserved favors from God because those who are chosen to be saved had nothing in themselves for why God decided to save them.
Unlike, Molinism which says that their god knows all things whether what will happen or what could happen, God in Scripture knows all things before they happened and that he had also predestined those things to happened. For God to know something is for God to predestinated it. Nothing happens outside of His knowledge. Whatever happens in this life happens because God knows it will happen. So those whom He did Predestined, He Called, Justified, and Glorified.