You may have heard that the largest religious group in America is the “nones,” those without a religious affiliation. In January of 2024, Pew Research stated that 28% of US adults are religiously unaffiliated. Of those, many are commonly called “fallen away” Catholics. In fact, in 2008, Pew estimated that 10% of the American population consisted of former Catholics. It’s almost a guarantee that if you’re reading this you know at least one person who has left the Catholic Church, and odds are good that you know at least one person in your family who has left the Church. Loving those around us and desiring their good and salvation, we face a rather pressing question: What happens to these people when they die? Is leaving the Catholic Church a mortal sin? Or, as my brother (who is no longer practicing) so eloquently put it, “Am I going to Hell?”

These questions touch on mysteries that no human being fully comprehends, but I think there is some value to be gained by contemplating what we do know. Specifically, it is my hope that by the end of this article, you will have a greater sense of clarity about questions of leaving the church and sin, as well as a greater sense of peace and encouragement in God, our loving Father, who is ever and eagerly searching for a glimpse of us prodigals on our way home.

To begin, let’s make sure that we’re clear on exactly what we’re asking when we inquire, “Is it a mortal sin to leave the Catholic Church?” I think three things deserve further meditation. The first is, what exactly is a mortal sin and what can we say about them here? The second is, what exactly do we mean when we speak of leaving the Church? And finally, what exactly do we mean by the Catholic Church in this context?

What is mortal sin?

Here’s a quick refresher on what mortal sin is (if you read this and are looking for more, there’s a great article here and a podcast here). A mortal (or deadly) sin has 3 qualities: the act itself is a grave matter, the one committing the sin has full knowledge of what they are doing and the moral ramifications, and full consent of the will. Let’s look at some examples to make these qualities clearer.

Grave Matter using the example of lying

NOT grave matter: Your co-worker asks how you’re doing. You are not doing particularly well, but you don’t want to talk about it, so you smile and say you’re fine.

Grave matter: Falsifying your timesheet at work.

Full Knowledge using the example of lying

LACKING full knowledge: A person is misled by something you said, but you believe yourself to be communicating clearly. You didn’t know that the message would not be received clearly.

With full Knowledge: You make a statement intending to mislead and know that it will be confusing or misleading.

Full Consent of the will using the example of lying

LACKING full consent: You are told you’ll be fired unless you misrepresent the status of a project to a client.

With full consent: There is no coercion or pressure, you misrepresent the status of a project to a client for financial gain.

What do we mean by “leaving” the Catholic Church?

With that in place, let’s turn to what it means to leave the Catholic Church. We can gain some insight into the question by looking at how we enter the Catholic Church in the first place. Our entry into the Catholic Church is accomplished through the Sacrament of Baptism. Baptism makes us members of the Body of Christ and incorporates us into the Church (CCC 1267). In addition, “Baptism seals the Christian with the indelible spiritual mark (character) of his belonging to Christ. No sin can erase this mark” (CCC 1272). So, practically speaking, what this means is that you can’t actually leave the Church. Baptism cannot be overwritten or removed. One way to think about this is to focus on how Baptism makes us children of God. A child can never stop being the child of their parents. Once we are God’s children, we can’t stop being so. 

With that in mind, what we typically mean when we talk about leaving the Church is akin to the prodigal son. We can leave the house. We can not show up for Mass. We can defy the expectations and teachings of right living. We can certainly stop believing in God and/or in any particular aspect of God, such as when a person concludes that God may well exist, but based on all the suffering in the world, He cannot be good. When we speak of leaving the Catholic Church, we are usually referring to something along these lines: actions that are contrary to Church teaching, such as not going to Mass on Sunday, breaking the commandments, or no longer believing in her teachings, from basic morals all the way up to the existence of God.

What do we mean by “the Catholic Church?”

Our final point of clarity is what we mean by the Catholic Church, and we have already alluded to it. The key distinction here is between the Church mystically as the Family of God, or the Body of Christ, and the Church as an earthly institution. The mystical reality cannot be changed since it is based on Baptism, which is indelible. The earthly institution is another story. This is what people usually mean by the “Catholic Church” in the context of leaving. One could get off the parish mailing list and refuse to attend Mass or other Catholic events and thus leave the earthly institution of the Catholic Church.

Conclusion: Is It A Mortal Sin To Leave The Catholic Church?

After all that prep, let’s put it together. Is it a mortal sin for someone to “leave the Catholic Church,” meaning they are no longer participating in the earthly institutional Church, the Mass, and sacraments, etc.? The Church is the source of saving grace given by God, so it certainly meets the grave matter criteria for mortal sin. If full knowledge and full will are present, then yes, we can say it is a mortal sin. HOWEVER, we as humans don’t have the ability to assess a person’s state of knowledge or volition. We can’t read hearts or minds. Therefore, we don’t know definitively if any specific person who has left the Church has committed mortal sin. Again, it’s a serious matter, and we should pray for all who have left the Church in any way, but we can’t know and shouldn’t assume mortal sin. The Church canonizes saints, meaning we know the person is in Heaven, but recognizing the boundlessness of God’s mercy and our own human limitations, the Church does no such thing regarding souls in Hell. Judge not.

God loves all his children and works tirelessly for their salvation. Even those away from the Church are his children. Hope for the salvation of all, and pray for the salvation of all. To my brother’s question, “Am I going to Hell?” I would respond, “I sure hope not, and there’s a God who loves you and gave his life to prevent it. I’d love to help you get in touch with him.”

Image: Photo by Atlas Green on Unsplash