The foundation, or basis of unity in Christ is Divine truth; the revealed Word.
17 "Sanctify them in the truth; Your word is truth.
18 "As You sent Me into the world, I also have sent them into the world.
19 "For their sakes I sanctify Myself, that they themselves also may be sanctified in truth.
20 "I do not ask on behalf of these alone, but for those also who believe in Me through their word;
21 that they may all be one; even as You, Father, are in Me and I in You, that they also may be in Us, so that the world may believe that You sent Me.
This is the word of truth delivered by the Holy Spirit as promised by Jesus.
13 "But when He, the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come.
This fits with what Paul is describing in the unit text of Ephesians 4:1-16. Note especially verse 15:
15 but speaking the truth in love, we are to grow up in all aspects into Him who is the head, even Christ,
In and through this body of revealed truth, the New Testament Scriptures, we will achieve the kind of unity for which Jesus prayed. He did not pray for unity based on something else (Democratic vote; compromise).
"Love" is not the basis of unity, rather the Word is. But love is one of the attitudes with which we teach and apply the truth, and the Word commands it, along with other godly attitudes.
2 with all humility and gentleness, with patience, showing tolerance for one another in love,
3 being diligent to preserve the unity of the Spirit in the bond of peace.
There are seven areas of Divine truth that Paul lists as the basis for preserving the unity of the Spirit.
4 There is one body and one Spirit, just as also you were called in one hope of your calling;
5 one Lord, one faith, one baptism,
6 one God and Father of all who is over all and through all and in all.
There is only one of each of these foundational basis' for unity. Also, we are talking not just being "one" in quantity but also in quality - i.e. it is not enough to be of one faith, we must be one in "the faith". It is not enough to worship one God, but must worship the true and living God.
Unity among Christians would include accepting as one standard for all the truth as revealed and confirmed by the Spirit through the apostles and prophets. Note that we are not to accept "every spirit" or "teaching" but only that given through the apostles and prophets.
1 John 4:1-6
Beloved, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world.
2 By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God;
3 and every spirit that does not confess Jesus is not from God; this is the spirit of the antichrist, of which you have heard that it is coming, and now it is already in the world.
4 You are from God, little children, and have overcome them; because greater is He who is in you than he who is in the world.
5 They are from the world; therefore they speak as from the world, and the world listens to them.
6 We are from God; he who knows God listens to us; he who is not from God does not listen to us. By this we know the spirit of truth and the spirit of error.
When all submit to the Lord's authority, there can be no division. There will be unity. When unity does not exist, someone is not truly submitting to the lordship of Jesus.
By Jon W. Quinn
The Front Page
From Expository Files 13.4; April 2006