We all find ourselves in the single vocation for a certain time in life, and for some, the single life may seem like the "last resort" - the state where anyone ends up who doesn't feel called to the priesthood or religious life, or who can't find a suitable spouse for marriage. But the single life is a vocation, a divine call to holiness, just like any of the other states of life. The Church needs lay Catholics who work in the world, and are available to dedicate themselves to their work and to the spread of the Gospel, without having to worry about supporting a family. Some people are in the single vocation for a short time, but others are called to the single vocation for their entire life.
Single people do great good in the Church. Since they are not bound to the commitments of a religious community, they have the flexibility to do all kinds of work in order to proclaim the Gospel. Since they do not have a family of their own to provide for, they can give their time to help care for other families which need their support. Single people also have more time available for study and prayer, so they can be great mentors and teachers to support people spiritually as well.
As with the married state, the single life is a vocation that is to be lived out in the midst of the world. The vocation of single Catholics is to represent Christ wherever they are and whatever they do, whether they are business people, teachers, writers, politicians, doctors, computer programmers, sales people, investors, lawyers, musicians, truck drivers, or lay missionaries. By the constant witness of a holy life, these people are lights shining out in the world, pointing out the way to God.
This witness in the world is a special form of preaching, and is a crucial component of the New Evangelization. The Catechism of the Catholic Church states, "Lay people also fulfill their prophetic mission by evangelization, 'that is, the proclamation of Christ by word and the testimony of life.' For lay people, 'this evangelization ... acquires a specific property and peculiar efficacy because it is accomplished in the ordinary circumstances of the world.' This witness of life, however, is not the sole element in the apostolate; the true apostle is on the lookout for occasions of announcing Christ by word, either to unbelievers...or to the faithful" (Catechism of the Catholic Church, 905).
Some single people take vows of chastity (single women can be consecrated as virgins according to a new rite in the Church), or enter secular institutes or other Catholic associations "in which the Christian faithful living in the world strive for the perfection of charity and work for the sanctification of the world especially from within" (Catechism of the Catholic Church, 928).