That much is true.
hence the reference we have here --
Romans 2
26 So if the uncircumcised man keeps the requirements of the Law, will not his uncircumcision be regarded as circumcision? 27 And he who is physically uncircumcised, if he keeps the Law, will he not judge you who though having the letter of the Law and circumcision are a transgressor of the Law? 28 For he is not a Jew who is one outwardly, nor is circumcision that which is outward in the flesh. 29 But he is a Jew who is one inwardly; and circumcision is that which is of the heart, by the Spirit, not by the letter; and his praise is not from men, but from God.
Romans 9
6 But it is not as though the word of God has failed. For they are not all Israel who are descended from Israel; 7 nor are they all children because they are Abraham’s descendants, but: “through Isaac your descendants will be named.” 8 That is, it is not the children of the flesh who are children of God, but the children of the promise are regarded as descendants.
Heb 8
8“Behold, days are coming, says the Lord,
When I will effect a new covenant
With the house of Israel and with the house of Judah;
9 Not like the covenant which I made with their fathers
On the day when I took them by the hand
To lead them out of the land of Egypt;
For they did not continue in My covenant,
And I did not care for them, says the Lord.
10 “For this is the covenant that I will make with the house of Israel
After those days, says the Lord:
I will put My laws into their minds,
And I will write them on their hearts.
And I will be their God,
And they shall be My people.
Like many other Christians on this board -- I am a New Covenant Christian..
In Gal 1:6-9 there is only ONE Gospel.
The NEW Covenant is that Gospel - it has adoption as children of God, AND forgiveness of sins.
Only ONE Gospel - and that Gospel was "preached to Abraham" Gal 3:8
All God's Children who are adopted into the family of God - born-again believers "know God" - just as Christ points out in John 14.
It is true for believers - for those who are born again.
Matthew 16
15 He saith unto them, But whom say ye that I am?
16 And Simon Peter answered and said, Thou art the Christ, the Son of the living God.
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.
1 John 2
26 These things I have written to you concerning those who are trying to deceive you. 27 As for you, the anointing which you received from Him abides in you, and you have no need for anyone to teach you; but as His anointing teaches you about all things, and is true and is not a lie, and just as it has taught you, you abide in Him.