Sometimes, we’re called to explain our Catholic beliefs using Scripture, often when talking with our Protestant friends. Other times, a historical approach works best, such as when we’re defending the reliability of the New Testament or Jesus’ resurrection to someone who may believe in God but is not a Christian.

No less important is the defense we must sometimes give for things that are logically prior to divine revelation. Theologians call these preambles of faith, and they include God’s existence, the divine attributes of God, the immortality of the human soul, and the natural moral law.

The tool that we use to account for these things is philosophy: the science of knowing the ultimate causes of things through natural reason. Catholics shouldn’t neglect this tool! We need to be able to present the preambles of faith for the good of unbelievers and fellow-believers alike.

For some unbelievers, the preambles of faith can be their first introduction to God, speaking to them in ways they can understand without faith. The Catechism affirms this in paragraph 39:

In defending the ability of human reason to know God, the Church is expressing her confidence in the possibility of speaking about him to all men and with all men, and therefore of dialogue with other religions, with philosophy and science, as well as with unbelievers and atheists.

Many other unbelievers, such as the New Atheists, routinely attack the preambles, making a robust defense necessary. To their credit, these New Atheists recognize that if they can falsify the foundations of faith, the whole house of religion comes tumbling down. If they’re willing to wrestle with these preambles of faith, we need to engage them on that front.

The preambles of faith can also provide a challenge for unbelievers to be more open to the revealed claims of Christianity. How so?

For starters, people who don’t think talk about God, the soul, or right and wrong are by definition closed off to faith. But if we can get them talking and thinking about these things, they will be more open to hearing what Christianity has to say about them. They may also begin to see that there’s a logical consistency between what reason says is true and the core beliefs of our biblical faith. For example: between a God who exists and a God who revealed himself because he loves us and wants to save us.

The preambles not only help us build a positive foundation for faith, they also can remove obstacles that stand in the way of embracing religious truths.

Most unbelievers, for instance, think that Christianity is just subjective feeling, a nice thought that makes believers feel good inside. But if we can show that God’s existence, the immortality of the human soul, and objective morality don’t just exist in our heads, that they are based on objective evidence that is accessible to reason, an unbeliever can begin to recognize that at least some Christian beliefs are not just feelings. And if some aren’t, then maybe others aren’t, too.

Another obstacle that many unbelievers face is a false understanding of what Christians mean by God. They’re used to thinking of God in human terms—as if he’s just another person like us, just disembodied and a lot bigger and stronger. It’s this type of thinking that leads critics to say things like, “You don’t believe in Zeus. So I just believe in one less god than you.”

Basic theistic philosophy can help them understand that the Christian God is not just one being (living on a cloud with a white beard) among many other beings within the finite world. Rather, he is being itself, not limited whatsoever in his existence. So rejecting deities like Zeus doesn’t match up with an atheist’s rejection of God.

As important as the preambles can be in dialogue with unbelievers, they are equally important to learn and stress for believers.

First, they protect believers from falling into the heresy of fideism: the belief that we can have certain knowledge of God only through divine revelation. The First Vatican Councilcondemned this idea, stating, “God, the source and end of all things, can be known with certainty from the consideration of created things, by the natural power of human reason.”

The preambles also help avoid incorrect interpretations of the Bible. For example, the Bible says that God has a hand and an ear (Isa. 59:6), along with arms (Isa. 53:1). But reason, by itself, can show that God is immaterial. This allows us to avoid misinterpreting biblical texts like these and know that they are merely describing God with human features—what’s called anthropomorphism.

The preambles also help us discern which aspects of other religions are and aren’t true. For example, inasmuch as another religion acknowledges the existence of one God who is infinite in power and the creator of heaven and earth, we can say that’s true. On the other hand, if a religion holds to a belief that all things are God—pantheism—we know that belief is false.

Knowing the philosophical foundations of our faith also strengthens our belief in Jesus and the truths he has revealed by showing how they’re compatible with reason. We can rest assured that our faith and our reason are coherent.

When St. Peter wrote in 1 Peter 3:15, “Always be prepared to make a defense to anyone who calls you to account for the hope that is in you,” he didn’t just mean biblical prooftexts or quotes from historians. So let’s keep our philosophical skills sharp, always ready to give an account for the reasonable foundations for our belief.

***This article was originally published by Catholic Answers Magazine Online on April 4, 2019