God saw all the descendants of Adam in Christ before all creation. Only Christ existed before creation:
According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love. having predestined us to the adoption of children by Jesus Christ to Himself, according to the good pleasure of His will -- Ephesians 1:4-5
1 John 5
10 He who believes on the Son of God has the witness in himself. He who does not believe God has made Him a liar, because he does not believe the record that God gave of His Son.
It's the Holy Spirit testifying to the one who believes, and to the one who does not believe. No one can make God a liar unless God has called him.
Firstly, Man does not call God. God calls man. God called Adam in the Garden of Eden after he sinned. Adam would not have looked for God. He was hiding from God.
God called Noah and told him (the Word of God) the end of all flesh had come before Him, and Noah believed what he heard, acted accordingly, and so was saved (faith comes by first hearing from God's Spirit).
God called Abraham and told him (the Word of God) that he would have a son, and in his seed all the families of the earth would be blessed, and Abraham believed God, and since then all the seed of Abraham who believe the Word of God like Abraham did, are saved, and we are saved through the seed of Abraham in Whom all the nations of the earth are blessed.
1 John 5
10 He who believes on the Son of God has the witness in himself. He who does not believe God has made Him a liar, because he does not believe the record that God gave of His Son.
The Holy Spirit first calls and testifies. Without the testimony of the Holy Spirit we will not either believe, or reject what we were not told by the Holy Spirit:
John 15
26 And when the Comforter has come, whom I will send to you from the Father, the Spirit of truth who proceeds from the Father, He shall testify of Me.
27 And you also shall bear witness, because you have been with Me from the beginning.
1 John 5
10 He who believes on the Son of God has the witness in himself. He who does not believe God has made Him a liar, because he does not believe the record that God gave of His Son.
We hear the Word of God. The Holy Spirit convicts us of our sin, and of God's righteousness, eternal judgment and salvation through Jesus.
It's the Holy Spirit testifying both to the one who believes, and to the one who does not believe. No one can make God a liar unless God has called him:
John 3
18 He who believes on Him is not condemned, but he who does not believe is condemned already, because he has not believed in the name of the only-begotten Son of God.
19 And this is the condemnation, that the Light has come into the world, and men loved darkness rather than the Light, because their deeds were evil.
Only Christ existed before creation:
According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love. having predestined us to the adoption of children by Jesus Christ to Himself, according to the good pleasure of His will -- Ephesians 1:4-5
Adam (mankind) did not exist before the foundation of the world, but Christ existed before the foundation of the world, therefore Adam (and all the descendants of Adam) is predestined to be saved by Christ through faith in Christ. But only the one who does not call God a liar when God calls him, but instead believes God and responds accordingly, is saved.
Otherwise (as in Calvinism) God purposed before creation to saw Adam in two so that only one part of the descendants of Adam would be called by the Holy Spirit, convicted and convinced by the Holy Spirit, so as to be saved.
1 John 5
10 He who believes on the Son of God has the witness in himself. He who does not believe God has made Him a liar, because he does not believe the record that God gave of His Son.
It's the Holy Spirit testifying to the one who believes, and to the one who does not believe. No one can make God a liar unless God has called him.