Catholics vs Atheists: How They Differ and What the Church Teaches

Catholicism DemystifiedSee all 45 articles in this series

Catholics believe in a personal God who created the world and gives each person an immortal soul. Atheists, as the group American Atheists puts it, “lack a belief in gods.” The Catholic Church calls atheism “a sin against the virtue of religion,” yet teaches that a person’s guilt for it “can be significantly diminished,” and invites atheists into dialogue.

The Church also teaches that salvation is open to people who, through no fault of their own, have not come to know God and, helped by his grace, try to live a good life. The two outlooks part over God, the soul, the source of right and wrong, and what happens at death. Yet when the Second Vatican Council took up atheism, it looked hard at believers too. Christians who live carelessly or teach the faith falsely, it said, “conceal rather than to reveal the true nature of God,” and nothing shows his presence more than “the brotherly charity of the faithful.” The question of atheism comes back to us.

The difference begins with God, and the rest follows from it. American Atheists, a national organization of atheists in the United States, says that atheism “is the answer to one question: Do you believe in gods?” and that “the only common thread that all atheists share is a lack of belief in gods.” Atheism by itself has no teaching about the soul or morality. For those questions the table gives the answers of humanism, as Humanists UK describes it. A humanist, in that description, “is therefore an atheist or agnostic,” though not every atheist calls himself or herself a humanist.

Question	Catholic Church	Atheists (American Atheists)
God	Can “be known with certainty” by reason (Catechism 36)	Atheists “lack a belief in gods”
Question	Catholic Church	Humanists (Humanists UK)
The world	God is “the origin and the end of the universe” (32)	“A natural phenomenon with no supernatural side”
The soul and death	The soul is created by God and “immortal” (366); a “particular judgment” follows death (1022)	“This life is the only life we have”
Right and wrong	A natural law known “by reason” (1954), its precepts “expressed in the Decalogue” (1955)	Choices “based on reason, empathy, and a concern for human beings and other sentient animals”
Meaning	Each person is “called to communion with God” (27)	People “give their own lives meaning”

The two sides meet on more ground than the table suggests. The Catechism holds that the natural law is “established by reason” and “extends to all men” (1956), so a Catholic and an atheist can reach the same conclusions about honesty or cruelty by different roads. Both also appeal to reason: the Church says the proofs of God are “converging and convincing arguments,” not “proofs in the natural sciences” (31), while humanists, in Humanists UK’s words, trust “the scientific method, evidence, and reason.” Catholics are themselves Christians, and on God, the soul and life after death they agree with Orthodox and most Protestant Christians; how Catholics differ from other Christians is a separate question.

The Church’s main statement is the Second Vatican Council’s Gaudium et Spes (1965), paragraphs 19 to 21, which the Catechism follows in paragraphs 2123 to 2126. The Catechism calls atheism “one of the most serious problems of our time” (2123). The Council was careful about the word. “The word atheism is applied to phenomena which are quite distinct from one another,” it said: some people expressly deny God, others think nothing can be known about him, others think the question meaningless, and still others reject “a fallacious idea of God” and “are by no means rejecting the God of the Gospel.” Atheism “results not rarely from a violent protest against the evil in this world” (19).

The Catechism’s judgment comes in two sentences. “Since it rejects or denies the existence of God, atheism is a sin against the virtue of religion,” with a reference to Romans 1:18. And “the imputability of this offense can be significantly diminished in virtue of the intentions and the circumstances” (2125). Imputability means how far an act can be charged to the person who does it. The Council did say that “those who willfully shut out God from their hearts and try to dodge religious questions are not following the dictates of their consciences, and hence are not free of blame” (19). It did not say that every atheist does this.

It also put part of the blame on believers. “Believers can have more than a little to do with the rise of atheism. To the extent that they are careless about their instruction in the faith, or present its teaching falsely, or even fail in their religious, moral, or social life, they must be said to conceal rather than to reveal the true nature of God and of religion” (2125, quoting Gaudium et Spes 19).

The Council also answered a claim it heard in modern atheism: that belief in God takes away human freedom, so that man must be “an end unto himself, the sole artisan and creator of his own history” (20). The Catechism says atheism “is often based on a false conception of human autonomy, exaggerated to the point of refusing any dependence on God,” and answers that “to acknowledge God is in no way to oppose the dignity of man, since such dignity is grounded and brought to perfection in God” (2126). The Council rejected atheism “root and branch,” yet it also said the Church “strives to detect in the atheistic mind the hidden causes for the denial of God” and, “conscious of how weighty are the questions which atheism raises,” believes “these questions ought to be examined seriously and more profoundly” (21).

The Church teaches that it is possible. The Second Vatican Council’s Lumen Gentium (1964) says: “Nor does Divine Providence deny the helps necessary for salvation to those who, without blame on their part, have not yet arrived at an explicit knowledge of God and with His grace strive to live a good life. Whatever good or truth is found amongst them is looked upon by the Church as a preparation for the Gospel” (16). The same paragraph says God is not “far distant from those who in shadows and images seek the unknown God,” words that echo Paul at Athens, who spoke of an altar “To The Unknown God” and of a God who is “not far from every one of us” (Acts 17:23, 27). The Catechism puts it this way: “Every man who is ignorant of the Gospel of Christ and of his Church, but seeks the truth and does the will of God in accordance with his understanding of it, can be saved” (1260).

The same documents set limits. The Catechism says that “they could not be saved who, knowing that the Catholic Church was founded as necessary by God through Christ, would refuse either to enter it or to remain in it” (846), and Lumen Gentium warns that “some there are who, living and dying in this world without God, are exposed to final despair” (16). The Church does not claim to know which of these describes a particular person. It holds that God can lead people to faith “in ways known to himself,” and that it still has “the obligation and also the sacred right to evangelize all men” (848).

It is not a Church term. People use it for someone raised Catholic who no longer believes in God but still feels Catholic by family, culture or habit. American Atheists counts such people as atheists: “If you call yourself a humanist, a freethinker, a bright, or even a ‘cultural Catholic’ and lack belief in a god, you are an atheist.”

Pew Research Center counts Americans who keep a Catholic tie without the faith, though not Catholic atheists as such. In a survey of 9,544 adults taken from 3 to 9 February 2025, it found that 9% of U.S. adults are “cultural Catholics,” who do not identify with Catholicism religiously but consider themselves Catholic “aside from religion,” for example ethnically or through family. Their religion may be another faith or none, and Pew does not report how many of them believe in God. Of these cultural Catholics, 83% seldom or never attend Mass and 81% never go to confession. Another 9% of adults are former Catholics who no longer consider themselves Catholic in any way. Asked for the main reason they are no longer Catholic, 9% of those who have left said they stopped believing in God or in religion.

Pew’s larger Religious Landscape Study of 2023 to 2024, which surveyed 36,908 adults, defines former Catholics more widely, as everyone raised Catholic who no longer identifies with the faith by religion, including some who still feel culturally Catholic. By that measure 13% of U.S. adults are former Catholics, against 19% who are Catholic, and 43% of Americans raised Catholic no longer identify as Catholic by religion. The nearest Pew comes to counting Catholic atheists is its finding that 7% of all adults were raised Catholic and are now religiously unaffiliated, a group that includes agnostics and people who say they are “nothing in particular” as well as atheists. In a further Pew survey of 8,937 adults in May 2025, about half of these unaffiliated former Catholics said a loss of belief was a major reason they left, and 81% said that believing they can be moral without religion is an extremely or very important reason they are unaffiliated.

Can a Catholic become an atheist?

A Catholic can stop believing in God, and the Church has a name for leaving the faith completely. Canon law defines apostasy as “the total repudiation of the Christian faith” (canon 751). In the Church’s teaching, though, baptism is not undone: it “seals the Christian with the indelible spiritual mark (character) of his belonging to Christ. No sin can erase this mark” (Catechism 1272). A Catholic who stops believing is, in the Church’s eyes, still baptized.

Canon law attaches an automatic excommunication to apostasy (canon 1364 §1), but no one incurs it who was under sixteen at the time, or who “through no personal fault was unaware that a penalty was attached” (canons 1323, 1324). Excommunication “impedes the reception of the sacraments,” and it is lifted through confession with the Pope, the local bishop or a priest they authorize, or with any priest when a person is in danger of death (Catechism 1463).

Doubt is a different matter. The Catechism distinguishes voluntary doubt, which “refuses to hold as true what God has revealed,” from involuntary doubt, which “refers to hesitation in believing, difficulty in overcoming objections connected with the faith, or also anxiety aroused by its obscurity” (2088). Struggling with belief is not the same as rejecting it.

Not quite, and the word “atheism” itself is used in two ways. American Atheists defines an atheist as someone who lacks belief in gods, and says that this “is not an affirmative belief that there are not gods.” Philosophers more often use the word for the claim that there is no God. The Stanford Encyclopedia of Philosophy notes that in the philosophy of religion “atheism” is “standardly used to refer to the proposition that God does not exist,” a sense preferred “by many (though not all) atheists in philosophy as well,” and it quotes the atheist philosopher William L. Rowe: atheism “proposes positive disbelief rather than mere suspension of belief.”

On agnosticism, American Atheists says: “Atheism is about what you believe. Agnosticism is about what you know.” The Catechism describes agnosticism in its own terms. In some forms the agnostic “postulates the existence of a transcendent being which is incapable of revealing itself”; in others he “makes no judgment about God’s existence, declaring it impossible to prove, or even to affirm or deny” (2127). It adds that agnosticism “can sometimes include a certain search for God,” but can also express “indifferentism” and “is all too often equivalent to practical atheism” (2128).

An atheist can be baptized only by coming to faith. Canon law requires an adult to have “manifested the intention to receive baptism,” to have been “instructed sufficiently about the truths of the faith and Christian obligations,” and to have been “tested in the Christian life through the catechumenate” (canon 865 §1). The Catechism says catechumens “are already joined to the Church” (1249).

An atheist can marry a Catholic in the Church, with permission. If the atheist was never baptized, the marriage is one of “disparity of cult,” which canon law makes invalid unless the diocese grants a dispensation (canon 1086). If the atheist was baptized in another church, it is a “mixed marriage,” one “between a Catholic and a baptized non-Catholic,” which needs “the express permission of ecclesiastical authority” (Catechism 1633, 1635). That permission makes the wedding lawful, while the dispensation for an unbaptized partner is “required for the validity of the marriage” (1635). If the atheist was baptized Catholic and has “notoriously rejected the Catholic faith,” a priest needs the diocese’s permission to assist (canon 1071). In each case the conditions of canon 1125 apply: the Catholic promises “to do all in his or her power so that all offspring are baptized and brought up in the Catholic Church,” the other spouse is told of that promise, and both are taught the purposes of marriage. The Catechism asks for “even greater circumspection” when a Catholic marries an unbaptized person (1633), because differences of faith can cause tension, “especially as regards the education of children” (1634). It quotes Paul’s First Letter to the Corinthians: “For the unbelieving husband is consecrated through his wife, and the unbelieving wife is consecrated through her husband.” It would be “a great joy,” it says, if this led to “the free conversion of the other spouse,” and it names what can prepare for it: “sincere married love, the humble and patient practice of the family virtues, and perseverance in prayer” (1637).

The verse is sometimes quoted that way: “The fool hath said in his heart, There is no God” (Psalm 14:1). The rest of the verse shows what the psalm means by a fool: “They are corrupt, they have done abominable works, there is none that doeth good.” The note on the psalm in the New American Bible, Revised Edition, published by the American bishops, explains that it “depicts the world as consisting of two types of people,” the fool, who “equals the wicked,” and “the company of the just.” In the psalm the fool is the wicked man, known by what he does rather than by an argument he holds.

Verses 2 and 3 continue: “The Lord looked down from heaven upon the children of men… They are all gone aside, they are all together become filthy: there is none that doeth good, no, not one” (14:2-3). It is Paul who applies these lines to everyone: he quotes them in Romans 3:11-12, having just said that “both Jews and Gentiles” are “all under sin” (Romans 3:9).

The Council called for cooperation and conversation. “While rejecting atheism, root and branch, the Church sincerely professes that all men, believers and unbelievers alike, ought to work for the rightful betterment of this world in which all alike live; such an ideal cannot be realized, however, apart from sincere and prudent dialogue.” It protested “against the distinction which some state authorities make between believers and unbelievers, with prejudice to the fundamental rights of the human person,” and added: “She courteously invites atheists to examine the Gospel of Christ with an open mind” (Gaudium et Spes 21). The remedy for atheism, it said, lies in “a proper presentation of the Church’s teaching as well as in the integral life of the Church and her members,” and “what does the most reveal God’s presence, however, is the brotherly charity of the faithful” (21).

Pope Benedict XVI gave the idea a name. Speaking to the Roman Curia on 21 December 2009, he said that “we, as believers, must have at heart even those people who consider themselves agnostics or atheists,” and added: “They do not want to see themselves as an object of mission or to give up their freedom of thought and will.” He proposed that the Church “open a sort of ‘Court of the Gentiles,’” named after the court of the Temple in Jerusalem where Gentiles, for whom God remained “the ‘unknown God,’” could come to pray, as a place for “a dialogue with those to whom religion is something foreign.” The Pontifical Council for Culture took up the idea, and on 25 March 2011 Benedict sent a video message for its inauguration in Paris to young people gathered outside Notre-Dame. He told them: “Those of you who are non-believers challenge believers in a particular way to live in a way consistent with the faith they profess.”

It is a fair challenge, and an old one. Jesus gave his followers the same charge: “Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven” (Matthew 5:16).

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• Do atheists celebrate Christmas?
• Do Catholics believe in evolution?
• Bible verses about doubt
• Bible verses about unbelievers and unbelief

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