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Of old you laid the earth's foundations; the heavens are the work of your hands. They perish, but you remain; they all wear out like a garment.
(Psalm 102: 26-27)

The heavens declare the glory of God; the sky proclaims its builder's craft.
(Psalm 19:2)

Ever since the creation of the world, God's invisible attributes of eternal power and divinity have been able to be understood and perceived in what he has made.
(St Paul's letter to the Romans 1:20)

For when the Gentiles who do not have the law [Mosaic law or 10 commandments] by nature observe the prescriptions of the law, they are a law for themselves even though they do not have the law. They show that the demands of the law are written in their hearts.
(St Paul's letter to the Romans 2:14-15)

You have made us for yourself, O Lord, and our hearts are restless until they rest in you.
(The Confessions of St. Augustine)


Those inquiring about or preparing to enter into the Catholic Church through RCIA have the opportunity to learn what it means to be Catholic. Being Catholic ultimately is about being united in love to the God who made us for himself, and who revealed himself definitively to us through the person of Jesus Christ. God gives all men the gift of his grace to believe in his goodness and mercy, but for many, before the gift of faith in Jesus Christ can be accepted, certain questions must be answered that can serve to remove obstacles to faith. The intellectual tradition of the Catholic Church (at times drawing on Jewish, Greek, and Muslim thought) going back 2000 years to St. Paul, has explored the nature of God and his relations with the world in the process of dealing with questions and objections to the faith. Using our natural reason, the Church teaches, we can come to know that God exists even though not all that has been revealed to us by God about himself can be discovered this way. Ultimately having knowledge of God's existence is not the same as faith in God. God wants us to have much more than simply correct ideas about him. God wants us to enter into a life transforming relationship with him, whereby we submit our whole lives to him in love, trust and obedience. Accordingly, having correct ideas about God is not enough, for that alone does not bring us to accept God's gift of loving friendship in faith. But having good reasons to believe that God exists certainly prepares us to accept God's gift of faith, for how can we believe and submit our lives to God if we doubt his very existence? Thus, our journey through RCIA begins with our examination of some of the arguments for God's existence based on human reason (that is, our natural capacity to use our rational minds to arrive at the truth). By studying these arguments we can not only determine that there are good reasons for belief in God, but we can also discover something about God's nature (i.e., the kind of God He is), for these arguments point not to an impersonal force but to a dynamic personal God of power, goodness, and truth.

Does God Exist?

The arguments for the existence of God are generally divided into two main categories: cosmological arguments, and arguments based on human nature and experience. The cosmological arguments get their data from without, that is, from the physical universe (cosmos means "orderly universe"). The arguments based on human nature get their data from within, that is, from our common nature and experience as human beings.

Since most of the arguments below will have to do with cause and effect, it will be helpful to spend a moment on the "law of causality." The law of causality basically states that every effect has a cause. This general law is based on our common sense view of nature, in which effects are regularly preceded by explanatory causes. In nature we do not observe uncaused effects, such as bunny rabbits appearing out of nowhere on empty tables. If such an event did occur, we would look for an explanatory cause, either physical or psychological (e.g. did it fall from the ceiling, was it transported by the crew of Star Trek, am I mentally ill etc...) rather than saying that's just the way reality operates. No one believes in the pop theory, that things just pop into existence for no reason at all. If effects were not preceded by explanatory causes, then we would live in an anything goes chaotic universe with no predictability wherein discovering anything at all about the universe through observation (i.e., science) would be impossible. Another way of referring to this common sense view is by what philosophers call the Principle of Sufficient Reason, which means that everything that is, has some adequate or sufficient reason why it is.

Below, five arguments for the existence of God will be presented. The first two are cosmological or first cause arguments, differing in that one argues that God is the cause of the beginning of the universes, and one argues that God is the continuing cause of the universe's existence. The third is another cosmological argument which states that God is the cause of the order and beauty (i.e. design) we find in the universe. After the three arguments from the created order are presented, two arguments based on human nature and experience will be explored, the moral argument and the argument from desire.

Each argument presented below takes the logical form of a deductive argument, with major and minor premises and the conclusion that follows. A sample of such an argument is the following:

1. All men are mortal (major premise -- general prinicple)
2. Socrates is a man (minor premise -- data from our experience that comes under the general principle)
3. Socrates is mortal (conclusion -- follows from applying general principle to the particular case)

After each argument is stated below, then a "Discussion" section follows where the premises are explained and evidence is presented for the premises. After the discussion section, a section follows on "God's attributes", where any discoveries about God's nature and attributes that were uncovered during the discussion of the argument are listed.

[Note: Many other versions of the first cause argument have been formulated, as well as other types of arguments for God's existence. See the 1st link at bottom for a fuller explanation of the arguments listed below, as well as 16 other arguments for God's existence from the Catholic philosopher Peter Kreeft.]

Cosmological Argument 1: God is the First Cause

1. Whatever begins to exist has a cause for its existence.
2. The universe began to exist.
3. Therefore, the universe has a cause and we call this cause God.

Discussion: This argument is simple and powerful. The first premise is usually granted because the principle of sufficient reason embodied in it is constantly verified and never falsified in our experience (has anyone ever observed something come from nothing?). It is the 2nd premise that requires evidence. In the last 100 years a great deal of scientific evidence has been amassed that supports the view that the universe had a beginning at a definite time in the past (e.g. evidence of an expanding universe, uniform cosmic background radiation, laws of general relativity etc...). But the laws of thermodynamics alone can briefly provide a scientific reason that makes it improbable to believe in an eternal universe. The 2nd law of thermodynamics (i.e. entropy) is a well established scientific law stating that over time the amount of unusable energy in a closed system increases. As unusable energy increases, usable energy decreases. When there is no more usable energy in a closed system, nothing else can happen (that is, no work can be done). The law of entropy explains why over time our house gets dirtier, not cleaner; why fallen objects break and do not reconstitute themselves, etc... Since the universe is all that there is, it is closed system. If the universe had no beginning, then an infinite amount of time would have elapsed and the usable energy in the universe would by now be depleted, resulting in a dead universe (see Psalm 102 above). But since the universe is obviously not dead (that is, there is still usable energy to do work) then the universe must not be eternal, or in other words, it began to exist at a definite time in the past.

There are also philosophical arguments against an eternal universe, including the impossibility of completing a task with an infinite number of steps. To complete such a task, or to reach any step along the way, an infinite or never ending amount of steps would precede it, but to complete a never ending series of steps is impossible. Looking at the time dimension we can see this same difficulty. For if the universe is eternal then it is infinitely old, in which case an infinite amount of time (e.g. seconds, minutes, hours) would have elapsed before reaching today, and since today has been reached, then the universe is finite in time, or in other words began to exist.

In summary then, if the universe began to exist, and something cannot come from nothing, then the universe had an uncaused cause for its beginning and we call that cause God.

God's Attributes: This argument from creation helps us discover several important things about God's nature. First, we see that God must be uncaused and eternal, for if he did begin to exist then he would require a cause for his existence (according to premise 1 above) and would therefore not be the first cause. Also, as creator of the universe in which time and matter began to exist, God is a purely spiritual being. Second, God must be all powerful to bring into existence a universe out of nothing, for if the universe is all there is, and God created it, then He created it out of nothing. Lastly, God must be a personal being and not merely an impersonal force. This is so because God willed or chose to create a universe with a definite beginning, rather than will that it exist eternally. This type of choice requires a being who can will certain things and not others, in other words, a personal being who can freely make choices.

Cosmological Argument 2: God is the Continuing Cause

1. If anything exists, it must either exist of itself (in which case it is called self-existent), or have its existence given to it by another (in which case it is called contingent or dependent, since it depends for its existence on another).
2. The universe - the collection of beings in space and time - exists.
3. The universe cannot account for its own existence.
4. Therefore, the cause of the universe is self-existent, and we call this cause God.

Discussion: This argument can be restated more simply as follows: a number of things, each of which owes its existence to something else, cannot be self-existent. Since each being in the universe is finite, changing and limited (look in the mirror to see one such being that exists now), then each being owes its existence to something else. Consider for instance what it takes right now for you or me to continue existing. We require food and drink and air and a certain climate etc... All these other causes that must exist simultaneously for us to exist also depend on other causes for their own existence as well. Just to have the air we breathe requires a certain type of atmosphere on a certain type of planet with a certain gravitational field in a certain type of solar system etc... And since these other causes (atmosphere, planet, solar system etc..) for our existence as well as the laws of nature that cause their operations could have been otherwise then they are or not at all, then they are finite and dependent and also owe their continuing existence to other causes. Since an infinite regress of finite causes is impossible to account for the existence of the universe (for you would always need one more finite cause), a first cause must exist that does not owe its existence to something else and that is not finite, not changing, and not limited in any way. Catholic philosopher Peter Kreeft puts it this way in his book Fundamentals of the Faith: "Dependent beings cannot cause themselves. They are dependent on their causes. If there is no independent being, then the whole chain of dependent beings is dependent on nothing and could not exist. But they do exist. Therefore there is independent being."

So in order for there to be dependent or finite beings in the universe at all, and for these beings to remain in existence, a cause outside the universe must exist that is independent or self-existent. This self-existent being is God.

God's Attributes: This argument helps us discover that God is self-existent, in that he doesn't depend for his existence on anything else. Another name for this type of existence is necessary existence, meaning that God cannot not exist. He exists necessarily and eternally, and is not dependent in any way. Such a being is infinite and perfect since He exists without any lack or limitation. Also, there can only be one God, since the existence of more than one infinite (without limit) being would mean that they are no longer infinite as each being would be a limit on the other's power and activity.

Cosmological Argument 3: God is the Cause of Design

1. There are only two possible ways in which a thing may come into being, by accident (or chance) or by design.
2. The characteristic of accident is disorder, whereas orderly arrangement shows design.
3. The universe shows an order so marvelous as to exclude accident.
4. Therefore, the universe must have been designed, and design requires an intelligent designer, and we call this designer God.

Discussion: This argument has wide appeal because it is constantly confirmed by our every day experience (see quote from St. Paul's letter to the Romans chapter 1 above). We see design everywhere because human beings are by nature intelligent designers. We build houses and cathedrals, develop languages and communication systems (like the Internet), compose symphonies and works of literature etc.. Since we are designers, and design involves intelligently adapting means to ends (that is, using things intelligently for a purpose), we can recognize such design reflected in the universe and in ourselves since its evidence is overwhelming.

This design is apparent both in looking at the physical universe itself, and at the biological creatures that inhabit it. Starting with the cosmos, it is staggering in its beauty and order. Who has not marveled looking at the stars at night or taken in an IMAX movie on the cosmic wonders of the universe? From a flowing river, to waves lapping on the beach, to the wind caressing a field of wheat, to the glory of a sunset, all this beauty is orchestrated by the laws of nature that govern the operations of the universe. These laws, as science has shown, are extremely fine tuned in such a way it appears so as to produce a universe capable of sustaining life, to the point where scientists speak of anthropic (anthropos is greek for human being) coincidences, or the uncanny ways in which the laws of nature appear geared to produce life. These laws are also beautiful in themselves, as expressed by the elegance of the mathematical equations that science has found that describe these laws. And one must ask, how is it that there is a universe at all that is capable of being described by mathematical equations? It seems that the designer wanted his creatures to be able to understand his creation, and through his creation to come to better know its Creator, and so He made a world capable of being known by his creatures, and endowed them with the intelligence in his image to understand the marvelous operations of the universe.

At the level of biology, design is also apparent. The DNA molecule alone, which is the basic building block of all life, contains a vast amount of complex information encoded within it. And evolutionary biology, which today attempts to replace an intelligent designer with the blind and purposeless processes of evolution by natural selection, cannot account for the complexity of the DNA molecule and the meaningful information it contains since DNA needs to exist before evolutionary processes can even begin. The odds against a DNA molecule coming together by chance out of the primordial soup of chemicals in earth's early period are astronomical, and that would be only the first step. DNA contains instructions for cell operations, but you need the rest of the cell to exist for DNA to do anything. The numbers become even more incalculable as you try to estimate the odds of getting DNA and all the other component parts of even the simplest cell coming together spontaneously. And there are many other instances of complex biological design (e.g. the human brain) that point to the need of a biological designer, and so it seems that both cosmic design and biological design point to an intelligent designer.

Finally, from a philosophical point a view an effect can't be greater than its cause, which would make it seem impossible that intelligence in the universe (such as human intelligence) could result from non-intelligent causes.

In summary then, the design that is evident in the cosmic order and beauty of the universe and in the biological complexity of its inhabitants reveals the intelligent designer we call God.

God's Attributes: This argument from design helps us to discover something more about God's nature, namely, that He is supreme beauty and intelligence itself as befits the designer of our beautiful and harmonious cosmos. It also shows that God is purposeful, in that He created and designed the universe and the creatures in it according to his own eternal plan. Most importantly, God has a plan for our lives. This plan we will discover more about as we progress through the RCIA year.

[Note: See the 2nd link at bottom for testimony from various eminent scientists about the marvelous design of the cosmos.]

Argument from Human Nature 1: God is the Cause of the Moral Law

1. An objective moral law exists only if God exists
2. An objective moral law exists.
3. Therefore, God exists.

Discussion: This argument cuts to the heart of what it is to be a human being (see quote from St. Paul's letter to the Romans chapter 2 above). Human beings, unlike animals, recognize a law that directs us by the voice of our consciences to do good and avoid evil. Even confirmed atheists agree that some actions are always wrong, that some actions are in fact bad moral actions (rape, murder, child abuse, torturing innocents etc...). But to assert that bad moral actions exist, then it must be assumed that good moral actions exist as well. And so an objective standard or law must exist to judge between good and bad actions. Since an objective moral law exists, then a moral lawgiver must exist.

Now if the moral law were merely subjective, that is just the opinion of an individual or group at a given time in history, then in no way can it be held that certain actions are always wrong. For if morality were concerned with subjective opinion only, then no binding moral laws would exist (for why should I listen to anyone else's opinion?). On the other hand, if there is real moral obligation, in the sense that we ought to do good and ought not to do evil, then where does this moral obligation or "ought" come from, if not God? Can blind purposeless matter (which if God does not exist is all that there is) produce an absolute moral obligation? Can the subjective opinions of an individual or a group obligate me to act morally? The answer is no to both questions. Dostoyevsky famously asserted, "If God does not exist, then everything is permitted." Without God there is ultimately no foundation for a binding objective moral law (even reason, for why should I be obligated to act reasonably?), and so to recognize a binding moral law is to recognize the cause of that law as well, and that is the transcendent moral lawgiver we call God.

So the moral law that is written in the hearts of all human beings can only have a transcendent cause and this moral lawgiver we call God.

God's Attributes: In addition to what we learned in the preceding sections about God's nature, namely that He is eternal, infinite, all powerful, personal, spiritual and intelligent, the moral argument shows that God is moral as well: He is goodness itself, as well as concerned that his human creatures act justly toward each other, recognizing the intrinsic worth of their fellow human beings who are made in God's image.

Argument from Human Nature 2: God is the cause of our Transcendent Desires

1. For every desire in created beings there exists something to fulfill that desire.
2. Human beings desire eternal life, love and happiness.
3. Therefore, a source of fulfillment exists for these human desires, and this we call God.

Discussion: For every human desire such as for food, drink, sleep, knowledge, sex etc... there exists something to fulfill that desire. If we hunger, there is food, if we thirst, there is drink etc.. But human beings have desire that transcend (go beyond) what our material universe can fulfill. Has anyone not experienced moments alone or with loved ones where time and eternity seem to meet (e.g. gazing at a beautiful sunset, in the embrace of a loved one, holding for the first time a newborn son or daughter etc...), timeless moments that we wish would last forever. In short, we desire eternal life, love and happiness. Since these desires exist, there must be something or someone to fulfill those desires. Christians believe that God made us for himself (see quote from St. Augustine above), and so implanted in us certain desires that only He could fulfill, so as to always point us to the end for which we were made, that is, everlasting peace, joy and happiness living in loving communion with God forever. Thus, our hearts desire for infinite love will be fulfilled by the God of infinite love who made us for himself.

God's Attributes: Here we discover that God is love, since He created us with a desire for everlasting love in our hearts that only He can fill.


We briefly looked at some traditional arguments for God's existence using natural human reason. We have seen that ultimately they all deal with facts about our universe and ourselves that can't be explained without a transcendent God, and so we believe that God exists. The arguments above can provide good reasons for belief in God, as well as tell us some important things about God's nature and attributes. But God wants us to know him intimately, and so He gave us something more than our own reason to rely on in coming to know him. He gave us divine revelation, whereby He speaks to us in history and finally becomes one of us in the person of Jesus Christ to fully reveal his infinite love for us. To be Catholic is to believe in the God who created us out of love, and redeemed us on a cross out of love so that we can live with him forever. That supreme mystery of God's love for us is what we begin to explore next in our journey through RCIA.

Additional resources on the Existence of God:

See printable version of this document in word format
Peter Kreeft: Twenty Arguments For The Existence Of God
Quotes from Scientists Regarding Design of the Universe