Our Church has been marked by outstanding examples of holiness in the lives of the saints of every age. No matter how dark the times may have been for our Church, there have always been those great saints through whom the light of Christ radiated. Yes, we are frail human beings, and at times we sin; yet, we repent of that sin and continue once again on the path of holiness. In a sense, our Church is a Church of sinners, not of the self-righteous or self-assured saved. One of the beautiful prayers of the Mass occurs before the Sign of Peace: "Lord, look not on our sins, but on the faith of your Church." Even though poor frail individual members of the Church fail and sin, the Church continues to be the sign and instrument of holiness.
The Church is also catholic. St. Ignatius of Antioch (c. 100) used this word meaning "universal" to describe the Church (Letter to the Smyrnaens). The Church is indeed Catholic in that Christ is universally present in the Church and that He has commissioned the Church to evangelize the world — "Go therefore an make disciples of all the nations" (Matthew 28:19). Moreover, we must not forget that the Church here on earth — what we call the Church militant — is united to the Church triumphant in Heaven and the Church suffering in Purgatory. Here is the understanding of the communion of saints — the union of the faithful in Heaven, in Purgatory, and on earth. Finally, the Church is apostolic. Christ founded the Church and entrusted His authority to His apostles, the first bishops.
The Church is also apostolic in that the deposit of faith found in both Sacred Scripture and Sacred Tradition was preserved, taught, and handed on by the apostles. Under the guidance of the Holy Spirit, the Spirit of truth, the Magisterium (the teaching authority entrusted to the apostles and their successors) has the duty to preserve, teach, defend, and hand on the deposit of faith. Moreover, the Holy Spirit protects the Church from error in its teaching authority. While over the course of time, the Magisterium has had to address current issues, such as nuclear war, euthanasia, in vitro fertilization, the same truth principles exercised under the guidance of the Holy Spirit prevail.