Paul says that "there is none that understandeth" and "there is none that seeketh after God."
There can be no true seeking after God until first God gives understanding.
However, the unregenerate state is described as a state impervious to understanding:
Eph. 4:18 Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart:
1 Cor. 2:14 But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.
2 Cor. 4:4 In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them.
In contrast regeneration is the reversal of this internal darkened, blinded, ignorant state. Regeneration is a CREATIVE ACT BY GOD where Jesus Christ is revealed by God in the heart:
2 Cor. 4:6 For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ.
Mt. 16:17 And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven.
Gal. 1:15 But when it pleased God, who separated me from my mother’s womb, and called me by his grace,
16 To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood:
Jn. 17:2 As thou hast given him power over all flesh, that he should give eternal life to as many as thou hast given him.
3 And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.
However, this revelation of God that comes with a new heart and spirit that is capable of understanding God is not found in the unregenerate but it most be GIVEN to them by God.
Deut. 5:29 O that there were such an heart in them, that they would fear me, and keep all my commandments always, that it might be well with them, and with their children for ever!
"Deut. 29:4 Yet the LORD hath not given you an heart to perceive, and eyes to see, and ears to hear, unto this day.
Jer. 31:33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.
Ezek. 36:26 [B]A new heart [/B]also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.
27 And I will put my spirit within you, and cause you to walk in my statutes, and ye shall keep my judgments, and do them.
Salvation is not in walking an isle, saying a prayer, making a decision for Christ - it is the revelation of Christ in you that changes you into a new creature:
Gal. 6:15 For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but a new creature.
Eph. 2:10 For we are his workmanship CREATED IN CHRIST JESUS unto good works.....