(Greek: katholikos, universal)
The term, in its primitive and non-ecclesiastical sense of universal, occurs in the Greek classics, and was freely used by the earlier Christian writers.
The combination, "the Catholic Church," is found for the first time in the Letter of Saint Ignatius to the Smyrneans, written about the year 110.
The words run:
"Wheresoever the bishop shall appear, there let the people be, even as where Jesus may be, there is the universal (catholic) Church."
The term continues to be found with ever-increasing frequency, in its technical sense, from this time forward; until by the 3rd century it was the commonly accepted formal title of the true Church, in contradistinction to all heretical or schismatic groups.
The theological significance underlying the term "Catholic" was fully drawn out during the struggle with the Donatists.
The Donatists had advanced a false conception of Church discipline and organization, and claimed to be the one true Church of Christ.
Saint Optatus and Saint Augustine in refuting them evolved the theology on the marks of the true Church, insisting especially on the note of Catholicity as a definite mark.
This note they pointed out was wholly inapplicable to the Donatist sect, which was confined to one section of Africa.
The theological discussion of the note of Catholicity, as applied to the true Church of Christ, is ordinarily concentrated on the concept of widespread diffusion throughout the world with a conspicuously great number of members.
It should be noted at once, however, that the true notion of Catholicity involves a twofold element: the material and the formal.
Not only should there be a notable diffusion throughout the world, which is the material element; but there should also be a definite unity in this diffusion.
In other words, that which is diffused, viz., the Church, should be one and the same everywhere.
Catholicity is a mode of unity; it is, as it were, the amplitude of unity.
The Catholicity of the Church, therefore, must be formal as well as material.
Many theologians of other communions, particularly of the Anglican Church, have taken the term "catholic" in the ordinary profane sense, as meaning unlimited comprehensiveness.
By applying this sense to the Church of Christ, they have evolved a notion of the Church Catholic, which to them signifies a Church which is able and willing to include all opinions however contradictory.
This sense of the term "catholic" is absolutely at variance with the sense intended by the Fathers of the Church, and by the theologians who have succeeded them during the centuries.
They used the term in a technical sense, to distinguish sharply the True Church from all religious organizations which claimed to be of Christ but which did not hold perfectly to His teachings.
It was used as a mark of opposition to every teaching which threatened unity and stability.
To use it now as a cover for disunity and instability directly contravenes the primary intention of that note which has always distinguished the Catholic Church from all others, viz., widespread diffusion with perfect unity.
New Catholic Dictionary