The English word church is related to the German word kirche and the Scottish word kirk, which both derive from the Greek term kyriakon, meaning the Lord's house. Confusingly, the Greek word in the New Testament that is usually translated as Church is ekklesia - the most basic meaning of which is a gathering, assembly, or congregation of people.(1)
The Greek word ekklesia itself derives from two root words: ek meaning out and kaleo meaning to call. We can therefore take the resulting word to mean a called-out assembly. In a general / non-theological sense ekklesia was typically used to describe a meeting that took place in a public space - people were in a sense 'called out' of their homes into a public meeting or gathering of people. Applied to the Church then ekklesia can thus be taken to mean a called-out assembly of believers in Christ. Followers of Jesus are called out of this world into a Kingdom that is not of this world (John 17:16, 18:36).
Church Universal
Strictly speaking in the New Testament the word church never refers to a building. The Universal Church (Catholic means Universal) is not limited to a particular denomination, communion, or creed, nor does it include Christians in name only who are actually outside of salvation in Christ. In the broadest sense of the word the Church is the invisible body of the elect throughout all of time - that is, all who were, are, and will be saved by grace through faith via the free gift of Jesus Christ.
Local Assemblies
Sometimes in Scripture the church in question is a local assembly of believers in a certain location - for example the Church in Jerusalem, Antioch or Corinth. In the early church believers gathered in homes for worship, fellowship, the Lord’s Supper, instruction, and ministry.(2) In Revelation chapters two and three seven letters are written by Jesus Himself to seven local churches in Asia Minor (modern day Turkey).
Upon This Rock
And I tell you, you are Peter, and on this rock I will build my church...Matthew 16:18
Jesus is building His Church. All too often man sets about to build the Church of Christ without bothering to involve Jesus in the process. Anything that man builds by his own strength using his own wisdom is not the Church that Jesus is building. It will not ultimately stand or last (more on this later).
Jesus is building His Church on this rock, so we need to discern what is meant by this rock. Historically three main views emerge:
1) Peter is the rock - This is the Roman Catholic position. Matthew 16:18 is given as support of the primacy of the Bishop of Rome and the Papacy.
2) This Rock refers to Peter's profession of faith. Support for this is taken from two verses earlier in Matthew 16:
[Jesus] said to them, “But who do you say that I am?”
Simon Peter replied, “You are the Christ, the Son of the living God.” (Matthew 16:15-16)
The Rock upon which Jesus is building His Church is Peter's profession and proclamation of faith. Thus according to this view Jesus builds His Church primarily through the confession and proclamation of Himslef as the Son of God who came and took on the form of human flesh.
3) Jesus Christ Himself is the Rock upon which the Church is built.
In the original Greek language there is clearly a word play happening here:
You are Petros (little stone) and on this petra (big rock) I will build my Church (Ekklesia):
In Koinē Greek, "petra" (πέτρα) generally implies a larger, more massive rock or a crag, while "petros" (πέρτρος) refers to a smaller stone or pebble. While the distinction isn't always sharply drawn, "petra" is understood to mean a larger, more substantial rock.(3)
The Bible itself identifies Jesus as the Rock. In 1 Corinthians 10:3, speaking of the Israelites in the desert after the Exodus from Egypt, Paul writes:
For they drank from the spiritual Rock that followed them, and the Rock was Christ (see Exodus 17:1-7).
Peter himself called Jesus Christ a living stone and, referencing Psalm 118:22 and Isaiah 28:16, a cornerstone, a stone the builders have rejected, a stone of stumbling, and a rock of offense:
As you come to him, a living stone rejected by men but in the sight of God chosen and precious, you yourselves like living stones are being built up as a spiritual house, to be a holy priesthood, to offer spiritual sacrifices acceptable to God through Jesus Christ. For it stands in Scripture:
“Behold, I am laying in Zion a stone,
a cornerstone chosen and precious,
and whoever believes in him will not be put to shame.”
So the honor is for you who believe, but for those who do not believe,
“The stone that the builders rejected
has become the cornerstone,”
and
“A stone of stumbling,
and a rock of offense.” (1 Peter 2:4-8)
Paragraph 552 of the Catechism of the Catholic Church, citing 1 Peter 2:4, calls Christ the living stone.
According to Scripture Christ is also the Cornerstone. Defining a cornerstone is therefore instructive. A cornerstone (aka a foundation stone or setting stone) is the first stone set in the construction of a masonry foundation. All other stones will be set in reference to this stone, thus determining the position of the entire structure.(4)
Jesus Christ is the beginning and the objective point of reference for the Church that He is building. No Christian should dispute this. Jesus is building His Church on the foundation of Himself.
Going back to the three options for defining who the rock is in Matthew 16:18, it doesn’t have to be either or.
Orthodox and Protestant/Evangelicals alike reject the Roman Catholic view that this verse establishes the Papacy, Apostolic Succession, and a strict hierarchy for a visible earthly Church. According to Ephesians 2:19-21 the household of God is built on the foundation of the apostles and prophets, with Jesus Christ Himself being the Cornerstone:
So then you are no longer strangers and aliens, but you are fellow citizens with the saints and members of the household of God, built on the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone, in whom the whole structure, being joined together, grows into a holy temple in the Lord.
Thus Jesus is the Big Rock (Petra) and Cornerstone of the Church. Peter is a little rock (petros), one of many little rock apostles/prophets that form the foundation. Though Petrine Primacy is not intended here, the Apostles were a gift given by Christ to equip the saints and to build up His Church (Ephesians 4:7-14). If Matthew 16:18 is applied less narrowly to all the Apostles then this line of reasoning holds up.
Putting all of this together, Peter's confession of faith (vs 16) - the profession and proclamation of the Lord Jesus Christ the Cornerstone - is the ground upon which church growth occurs. Views two and three outlined above both hold up. It's not either / or but both / and.
The practical question for us then is this: Are we building the same Church that Jesusis building? If we are building upon any foundation other than Jesus Christ and the profession and proclamation of Him as our Savior and Lord, then we are not building Christ's Church. We can be busy playing Church. We can impliment man-made programs to increase our numbers. We can have an emotional experience. But that doesn't mean we are playing any part in building the Church that Christ is building.
(1) The New Testament was originally written in Koine Greek. Koine Greek was the Greek spoken by regular people in the marketplace. By contrast Classical Greek was more prestigious and was used by Philosophers, in higher forms of literature, etc.
(2) The Moody Handbook of Bible Theology, Paul Enns, 347-354.
(3) Google search, May 18, 2025:
(4) Grok search, May 18, 2025
https://x.com/i/grok/share/JJKV50DKmumJz7ccDkyNphAKa