Strong's Con,NT# 572 from G573; singleness, i.e. (subjectively) sincerity (without dissimulation or self-seeking), or (objectively) generosity (copious bestowal):—bountifulness, liberal(-ity), simplicity, singleness.
A. Take the doctrine of "circumcision" for example.
Certain "men which came down from Judaea taught the brethren, and said, Except ye be circumcised after the manner of Moses, ye cannot be saved. When therefore Paul and Barnabas had no small dissension and disputation with them.
1. Where did circumcision begin?
a. Began with Abraham (Gen.17:9-14) b. It was a Covenant that God made with Abraham c. It was a "token." - a signal (literally or figuratively), as a flag, beacon, monument, omen, prodigy, evidence, etc.:—mark, miracle, (en-) sign, token.) [Strong's OT.#226 ʼôwth, oth;] d. Those that refused circumcision were cut from their people if (Gen.17:14; 21:4 Exod.4:26) Note: The Children of the flesh of Abraham (Rom.9:1-8) were (cut) broken off (Rom.11:20-25) because they rejected the true circumcision of Christ. (Rom.2:28-29, Gal.6:15-16)
e. Note: The Gentiles were the uncircumcision (Eph.2:11,)
2. After the Cross circumcision continues in it's reality, which is Water Baptism.
"Ye (you) are complete in him, which is the head of all principality and power: In whom (Jesus Matt.5:17-19, Rom.3:21-31) also ye are circumcised with the circumcision made without hands, in putting off (Col.2:11-12) the body of the sins of the flesh by the circumcision of Christ: Buried with him in baptism, (Rom.6:1-11) wherein also ye are risen with him through the faith of the operation of God, who hath raised him from the dead." (Col.2:11-12) Note: How the serpent is beguiling the mind of these Pharisees into corrupting scripture to ignore the Cross.
Conclusion: Circumcision is still REQUIRED in it's reality. Don't let serpent beguile you from going through the (singleness / simplicity) of the Cross and be "removed from the Gospel" (Gal.1:6-9)
B. Christ must preeminent.(Col.1:18; 2:6-8) 1. He is before all things (John.1:1-14, Heb.1:1-2; 11:1-3) 2. By Him all things consist (John.1:1-3, Col.1:17) 3. He is the head of the Church (Eph.1:22-23, Col.1:18) 4. The firstborn (Col.1:15-18, Matt.1:25, Rom.8:29, Heb.11:28; 12:23) 5. By Him all things are reconciled (by the Cross) on earth or in heaven ( 6. Christ is our measurement to attain to (Eph.4:11-16) 7. Follow me as I follow Christ (1Cor.11:1) 8. Everything points to Christ. (Heb.9:1-10) 9. NT God has spoken by His Son. (Heb.1:1-2)
(Singleness - Everything must come through the Cross)