'I believe in One, Holy, Catholic and Apostolic Church.'
- Nicene Creed, the Symbol of Faith
These characteristics of the Church: unity, holiness, conciliarity and apostolicity, derive from the very nature of the Church and its purpose.
The Church is One and unique, in that it is founded by, and in, Christ the Theanthropos, Who is both One, and unique. The unity of the Church inevitably follows from Christ's theanthropic unity in our Lord Jesus Christ. It is not divided in any sense, as it is one unique theanthropic organism and organisation.
This uniqueness and unity which is described by St Justin Popovic, is also proclaimed by St Paul:
'for other foundation can no man lay than that is laid, which is Jesus Christ.' (1 Cor 3:11)
By nature, and as a unique organisation, the Church is 'in fact, a theanthropic workshop for the sanctification of men and, through them, of all creation.' The Church is Holy as it is indeed the body of Christ, of whom the Lord Jesus Christ is Himself the immortal Head, and the Holy and Life-Giving Spirit is the immortal soul. For this reason, its teaching, its blessings, its sacraments, its virtues, its powers, and all that it provides and fulfils, are all Holy.
Because the Church consists of sinners, does it become less Holy?
St Justin states that by no means does the fact sinners make up the body of Christ mean its Holiness is somehow decreased; because the Lord Jesus is its Head, and the Holy Spirit its soul. In them, the Church's divine sacraments, teaching and virtues are unalterably Holy. The vineyard of Christ protects and teaches sinners, in order to move them in repentance towards spiritual healing, transfiguration and salvation.
Archimandrite Dr Justin Popovic, The Orthodox Church and Ecumenism (Birmingham: Lazarica Press, 2000) 47-49.