The apostolate of the laity under the guidance of the hierarchy. Since Catholic Action became an established feature of the Church in modern times, it has undergone several stages of development. The necessary role of the laity in the Church's mission of evangelization and education is one of the principal doctrines of the Second Vatican Council. They are seen as not mere supplements to make up for what is wanting among the clergy, nor even as mere assistants. Their function in the Church's mission to the world is co-ordinate with that of priests and religious, while they serve in the corporal and spiritual works of mercy in deference to the divinely established hierarchy. Consistent with the Church's development of the concept of subsidiarity, lay people are to be given every opportunity to make their own distinctive contribution to the Catholic apostolate. Moreover, with the progress in social communications they are to work co-operatively among themselves in groups and organizations that are always respectful of the local hierarchy but also conscious of their larger, even international responsibility (under the Holy See) to Christianize all of human society.