The Nicene Creed identifies the Church of Christ by four marks: she is one, holy, catholic, and apostolic. Only one Church fits that description.
The description in the Creed is a description of our true home. It is a lighthouse, a roadmap, a clear marker for searchers and travelers.
One. Is any other church so one that all schisms that occur in that church are clearly schisms between the old and the new, between the Church that comes from Christ and one that comes from man, between the one Church that existed from the beginning and the breakaway group? The Catholic Church is the one church all other churches have to break away from.
Is any other church one through the ages, teaching the same dogmas, never going back on herself, never saying “oops” in matters of theological or moral dogma?
Is any other church one in space as well as time? Is any other church catholic, i.e., universal? As Chesterton says, how can a missionary ask an Outer Mongolian to become a Southern Baptist?
Apostolic. Is any other church apostolic in teaching both what the apostles taught and with the authority Christ gave to them and their successors? Is any other church apostolic in sacramental succession? Among Protestant churches, only the Anglican Church even claims apostolic succession, but they broke it when Henry VIII broke with Rome, with her bishops, and with her bishops’ ability to ordain other bishops in the apostolic succession that began with St. Peter and always traced its lineage back to him.
Universal. Does any other church claim the name catholic, meaning “universal”? She is universal in many senses: for all men, for all the world, for all times, for all cultures, and teaching all that Christ and the apostles taught.
Holy. But what about holy? The Church contains many notable, even scandalously famous, sinners. A couple of them were even popes!
The Church’s claim to holiness is not that Catholics are all holy people, or that Catholics are holier than other Christians. Her claim is that she herself is holy (holy means “set apart,” implying “set apart by God”), and therefore the source of holiness. You can’t give what you don’t have: that is the principle of causality. The Church is the saint maker.
The meaning of life and the nonnegotiable divine command, which God repeated over and over again when He gave His law to His chosen people, is: “You shall be holy; for I the Lord your God am holy” (Lev. 19:2).
Christ did not mitigate this essential command but repeated it and made its absoluteness even more explicit, closing the door, the “escape clause,” that we naturally add: “to the best of your ability — just try a little harder.” He said: “You, therefore, must be perfect, as your heavenly Father is perfect” (Matt. 5:48). That is the reason for Purgatory. God will not take us out of the oven if we are only half-baked.
The Church is our connector with Christ. To break that connector is to break with Christ. To refuse the body is to refuse the Head. That is why St. Thomas More embraced martyrdom rather than approve Henry’s break with Rome when Rome would not approve his divorce. Here is how he explained to his beloved daughter Margaret why he couldn’t compromise his conscience just a little bit to save his life and the safety of his family, in A Man for All Seasons:
More: If we lived in a state where virtue was profitable, common sense would make us good . . . and we’d live like animals or angels in the happy land that needs no heroes. But since in fact we see that avarice, anger, envy, pride, sloth, lust, and stupidity commonly profit far beyond humility, chastity, fortitude, justice and thought . . . why, then perhaps we must stand fast a little, even at the risk of being heroes.
Margaret: But in reason! Haven’t you done as much as God can reasonably want?
More: Well . . . finally . . . it isn’t a matter of reason; finally, it’s a matter of love.
Why does it take a Church (the Church) to make saints? Because we can’t do it ourselves. We can’t lift ourselves up by our own bootstraps. The physician can’t heal himself. The tiger can’t change his stripes.
But even though holiness is not a do-it-yourself thing, even though we need God and grace, why do we need the visible, concrete, historical, sacramental, material Church? Why can’t our relationship with God and our dependence on God be one-on-one and spiritual?
Because Christ is not one-on-one and spiritual. Christ gathered an apostolic college, and founded a visible Church, and gave her His literal body and blood, both on the Cross and in the Eucharist. Catholics paint with His grain, not against it. Catholics just deliver His mail; they don’t correct it.
God makes saints, but He does it through Christ, and Christ does it through His body, which is His Church.
Of course, it’s done by the Holy Spirit, and it’s spiritual. It’s also done by Christ’s incarnate body, and it’s material. Why? Because it’s done in man and for man, and man is not an angel but is always both spiritual and material.
To attain and achieve the meaning of life (of your life), be a saint.
To be a saint, go to Christ. To get wet, go where it’s raining. To get holy, go where Christ is.
Where is Christ? In His body, not “out of the body.” To go to Christ, go to His body, His Church.
Christ is in non-Catholics, too, spiritually, but not materially, not sacramentally, not Eucharistically. Why settle for a little lifeboat when you can have the whole ark?
This article is adapted from a chapter in Forty Reasons I Am a Catholic by Dr. Peter Kreeft which is available from Sophia Institute Press. 
Art for this post on the four marks of the Church: Cover of Forty Reasons I Am a Catholic used with permission; Entrega de las llaves a San Pedro (Giving of Keys to Saint Peter), Pietro Perugino, between 1481 and 1482, PD-US author’s term of life plus 100 years or less, Wikimedia Commons.
Read more about the role of the Church HERE.
This article is reprinted with permission from our friends at Roman Catholic Spiritual Direction.
Peter Kreeft, Ph.D., is a professor of philosophy at Boston College and also at the King's College (Empire State Building) in New York City. He is a regular contributor to several Christian publications, is in wide demand as a speaker at conferences, and is the author of over 55 books. Dr. Kreeft is a convert to the Catholic Church from reformed Protestantism. He earned an A.B. degree from Calvin College, an M.A. and Ph.D. from Fordham University, followed by post-doctoral work at Yale University. He has received several honors for achievements in the field of philosophy, including the Woodrow Wilson Award, Yale-Sterling Fellowship, Newman Alumni Scholarship, Danforth Asian Religions Fellowship, and a Weathersfield Homeland Foundation Fellowship.