Allow me to offer a positive definition of the Church of Christ. Before I do, I need to be a little clearer. The Gospel defines the church and not the other way around. Since Protestants used to believe the Doctrine of Justification is definitional, it was believed that Justification in the Protestant sense was definitional of a standing or falling church.
I agree with John Calvin that within the Roman Communion there exists a true church, Rome however is not. She had clearly opposed Justification by Faith Alone at the Council of Trent. The Pope has recently affirmed prior councils. Therefore she remains outside of the Biblical definition of a
true church.
For a definition of church and how she is to function, here is the chapter
Of the Church from the LBCF 1689:
1. The Catholick or universal Church, which (with respect to the internal work of the Spirit, and truth of grace) may be called invisible, consists of the whole (a) number of the Elect, that have been, are, or shall be gathered into one, under Christ the head thereof; and is the spouse, the body, the fulness of him that filleth all in all.
a Heb. 12.23. Col. 1.18. Eph. 1.10,22.23. & ch. 5.23,27,32.
2. All persons throughout the world, professing the faith of the Gospel, and obedience unto God by Christ, according unto it; not destroying their own profession by any Errors everting the foundation, or unholyness of conversation, (b) are and may be called visible Saints; (c) and of such ought all particular Congregations to be constituted.
b 1 Cor. 1 2. Act. 11.26.
c Rom. 1.7. Eph. 1.20,21,22.
3. The purest Churches under heaven are subject (d) to mixture, and error; and som have so degenerated as to become (e) no Churches of Christ, but Synagogues of Satan; nevertheless Christ always hath had, and ever shall have a (f) Kingdome in this world, to the end thereof, of such as believe in him, and make profession of his Name.
d 1 Cor. 15. Rev. 2. & ch. 3. [Note]
e Rev. 18.2. 2 Thes. 2.11,12.
f Mat. 16.18. Ps. 72.17. & Ps. 102.28. Rev. 12.17.
4. The Lord Jesus Christ is the Head of the Church, in whom by the appointment of the Father, (g) all power for the calling, institution, order, or Government of the Church, is invested in a supream & soveraigne manner, neither can the Pope of Rome in any sense be head thereof, but is (h) that Antichrist, that Man of sin, and Son of perdition, that exalteth himself in the Church against Christ, and all that is called God; whom the Lord shall destroy with the brightness of his coming.
g Col. 1.18. Mat. 28.18,19.20. Eph. 4.11,12.
h 2 Thes. 2.3-9.
(A note on this paragraph)
5. In the execution of this power wherewith he is so intrusted, the Lord Jesus calleth out of the World unto himself, through the Ministry of his word, by his Spirit, (i) those that are given unto him by his Father; that they may walk before him in all the (k) ways of obedience, which he prescribeth to them in his Word. Those thus called he commandeth to walk together in particular societies, or (l) Churches, for their mutual edification; and the due performance of that publick worship, which he requireth of them in the World.
i Joh 10.16. chap. 12,32.
k Mat. 28.20.
l Mat. 18.15-20.
6. The Members of these Churches are (m) Saints by calling, visibly manifesting and evidencing (in and by their profession and walking) their obedience unto that call of Christ; and do willingly consent to walk together according to the appointment of Christ, giving up themselves, to the Lord & one to another by the will of God, (n) in professed subjection to the Ordinances of the Gospel.
m Rom. 1.7. 1 Cor. 1.2.
n Act. 2.41,42. ch. 5.13.14. 2 Cor. 9.13.
7. To each of these Churches thus gathered, according to his mind, declared in his word, he hath given all that (o) power and authority, which is any way needfull, for their carrying on that order in worship, and discipline, which he hath instituted for them to observe; with commands, and rules, for the due and right exerting, and executing of that power.
o Mat. 18.17,18. 1 Cor. 5.4,5. with v.13. 2 Cor. 2.6,7,8.
8. A particular Church gathered, and compleatly Organized, according to the mind of Christ, consists of Officers, and Members; And the Officers appointed by Christ to be chosen and set apart by the Church (so called and gathered) for the peculiar Administration of Ordinances, and Execution of Power, or Duty, which he intrusts them with, or calls them to, to be continued to the end of the World are (p) Bishops or Elders and Deacons.
p Act. 20:17, with v.28. Phil. 1.1.
9. The way appointed by Christ for the Calling of any person, fitted, and gifted by the Holy Spirit, unto the Office of Bishop, or Elder, in a Church, is, that he be chosen thereunto by the common (q) suffrage of the Church it self; and Solemnly set apart by Fasting and Prayer, with imposition of hands of the (r) Eldership of the Church, if there be any before Constituted therein; And of a Deacon (s) that he be chosen by the like suffrage, and set apart by Prayer, and the like Imposition of hands.
q Act. 14.23: See the original.
r 1 Tim. 4.14.
s Act. 6.3.5.6.
10. The work of Pastors being constantly to attend the Service of Christ, in his Churches, in the Ministry of the Word, and Prayer, (t) with watching for their Souls, as they that must give an account to him; it is incumbent on the Churches to whom they Minister, not only to give them all due respect, (u) but also to communicate to them of all their good things according to their ability, so as they may have a comfortable supply, without being themselves (x) entangled in Secular Affairs; and may also be capable of exercising (y) Hospitality toward others; and this is required by the (z) Law of Nature, and by the Express order of our Lord Jesus, who hath ordained that they that preach the Gospel, should live of the Gospel.
t Act. 6.4. Heb. 13.17:
u 1 Tim. 5.17,18. Gal. 6.6,7.
x 2 Tim. 2.4.
y 1 Tim. 3.2.
z 1 Cor. 9.6.-14.
11. Although it be incumbent on the Bishops or Pastors of the Churches to be instant in Preaching the Word, by way of Office; yet the work of Preaching the Word, is not so peculiarly confined to them; but that others also (a) gifted, and fitted by the Holy Spirit for it, and approved, and called by the Church, may and ought to perform it.
a Act. 11.19,20,21. 1 Pet. 4.10.11.
12. As all Believers are bound to joyn themselves to particular Churches, when and where they have opportunity so to do; So all that are admitted unto the priviledges of a Church, are also (b) under the Censures and Government thereof, according to the Rule of Christ.
b 1 Thes. 5.14. 2 Thes 3.6.14,15.
13. No Church-members upon any offence taken by them, having performed their Duty required of them towards the person they are offended at, ought to disturb any Church order, or absent themselves from the Assemblies of the Church, or Administration of any Ordinances, upon the account of such offence at any of their fellow-members; but to wait upon Christ, (c) in the further proceeding of the Church.
c Mat. 18.15.16,17. Eph. 4 2,3.
14. As each Church, and all the Members of it are bound to (d) pray continually, for the good and prosperity of all the Churches of Christ, in all places; and upon all occasions to further it (every one within the bounds of their places, and callings, in the Exercise of their Gifts and Graces) so the Churches (when planted by the providence of God so as they may injoy opportunity and advantage for it) ought to hold (e) communion amongst themselves for their peace, increase of love, and mutual edification.
d Eph. 6.18. Ps. 122.6.
e Rom. 16.1,2. 3 Joh. 8,9,10.
15. In cases of difficulties or differences, either in point of Doctrine, or Administration; wherein either the Churches in general are concerned, or any one Church in their peace, union, and edification; or any member, or members, of any Church are injured, in or by any proceedings in censures not agreeable to truth, and order: it is according to the mind of Christ, that many Churches holding communion together, do by their messengers meet to consider, (f) and give their advice, in or about that matter in difference, to be reported to all the Churches concerned; howbeit these messengers assembled are not entrusted with any Church-power properly so called; or with any jurisdiction over the Churches themselves, to exercise any censures either over any Churches, or Persons: or (g) to impose their determination on the Churches, or Officers.
f Act. 15.2,4,6. & 22,23.25.
g 2 Cor. 1.24. 1 Joh. 4.1