At a recent Adult Bible Study class at my church, I gave a presentation on some deductive proofs of God’s existence. My outline is below. I’ve edited it to simplify a few things, and incorporate some good ideas pointed out by the audience. In several places, my discussion closely follows Kreeft and Tacelli, Handbook of Christian Apologetics.
From the Internet Encyclopedia of Philosophy: “An argument is a connected series of statements or propositions, some of which are intended to provide support, justification or evidence for the truth of another statement or proposition. Arguments consist of one or more premises and a conclusion. The premises are those statements that are taken to provide the support or evidence; the conclusion is that which the premises allegedly support.”
There are two kinds of arguments: “A deductive argument is an argument in which it is thought that the premises provide a guarantee of the truth of the conclusion. In a deductive argument, the premises are intended to provide support for the conclusion that is so strong that, if the premises are true, it would be impossible for the conclusion to be false.
An inductive argument is an argument in which it is thought that the premises provide reasons supporting the probable truth of the conclusion. In an inductive argument, the premises are intended only to be so strong that, if they are true, then it is unlikely that the conclusion is false.”
Most of the arguments for God’s existence are deductive arguments. Here is an example deductive argument:
- Any person born in a state in the United States is a citizen of the United States.
- North Carolina is a state in the United States.
- Sarah was born in North Carolina.
- Therefore, Sarah is a citizen of the United States.
If the first three statements are true, the conclusion (statement 4) is guaranteed to be true.
A deductive argument can be attacked in one of two ways. First, you can question the truth of the premises. For example, in the Sarah argument above, you might demand proof that Sarah was born in North Carolina. If it turns out Sarah was born in England, the truth of the conclusion is not guaranteed. Note that even thought the argument would fail in this case, it doesn’t follow that statement 4 is false. Perhaps Sarah is a naturalized citizen. To show that an argument is flawed does not necessarily demonstrate that its conclusion is objectively false.
A second line of attack is to question the connection between the statements of the argument. Here is an example of a flawed deductive argument:
- A dog is an animal with four legs.
- Sylvester (see the picture below) is an animal with four legs.
- Therefore, Sylvester is a dog.
Obviously, something is wrong with this argument! The problem is that statements 1 and 2 are not connected in the right way to gaurantee the truth of statement 3.
As we examine deductive arguments for God’s existence, we must consider the truth of the premises and the connections between them.
The arguments for God’s existence fall into several broad categories:
- Cosmological arguments
- Teleological arguments
- Ontological arguments
- Psychological arguments
A cosmological argument is based on empirical evidence , i.e., what we observe about the Universe. Two well-known cosmological arguments are the Kalam Argument and the Argument from Contingency.
The Kalam Argument
- Whatever begins to exist has a cause for its existence.
- The Universe began to exist.
- Therefore the Universe has a cause for its existence.
This argument is easy to criticize. First, we cannot be certain statement 2 is correct. The Big Bang theory seems to support it, but it seems the Big Bang theory doesn’t provide the kind of deductive certainty the Kalam argument attempts to provide. It’s possible the universe has existed forever. On the other hand, statement 2 is unquestionably reasonable. While statement 3 is guaranteed if statements 1 and 2 are true (the argument is valid), we cannot be certain the cause of the Universe’s existence is the personal God of Christianity. Kreeft and Tacelli argue that we can be certain the cause is a personal agent, unbounded by time and space, that chose to create the universe. I leave it to the reader to investigate this further.
The Argument from Contingency
- Definition: an object is contingent if its existence is dependent on the existence of something else.
- Every object in the universe is contingent.
- Therefore, the universe itself is contingent: its existence depends on the existence of something else.
- The thing on which the universe’s existence depends cannot be part of the universe, or be bounded by space and time.
- Therefore, the universe’s existence depends on something that stands outside the universe, unbounded by space and time.
There are several possible criticisms of this argument. The connection between 2 and 3 is not clear. Does statement 3 follow immediately from statement 2? Some see the fallacy of composition here. On the other hand, statement 3 has not been disproven, and it seems likely to be true. One can ask for proof of statement 4; Kreeft and Tacelli consider this while discussing the argument in a slightly different form. Finally, as with the Kalam argument, we cannot be certain that statement 5 refers to the personal God of Christianity.
Despite the problems, I find the argument from contingency the most compelling of the deductive arguments for God’s existence.
A teleological argument is based on the complex interdependencies that exist in nature. Teleological arguments are often called “design arguments.” The most famous teleogical argument is the Argument from Design. While there is considerable overlap with Intelligent Design, a discredited alternative to biological evolution, there is an important difference between the two.
The Argument from Design
- The Universe displays an order and regularity that inspires wonder.
- It is normal for many different things to work together to produce a valuable end.
- Either this intelligible order is the product of blind chance or of intelligent design.
- It is not the product of blind chance.
- Therefore, it is the product of intelligent design.
Intelligent Design rejects statement 2, asserting that it’s impossible for the Universe to evolve complex biological systems such as human beings. In doing so, ID must arrive at statement 5 through a different route. To me, this creates an entirely different kind of argument. Atheists will emphasize statement 2 to the point of rejecting God’s existence: the Universe generates complexity because that’s just the way the Universe works.
Almost all criticism is focused on statement 3, “Either this intelligible order is the product of blind chance or of intelligent design.” Most critics point out that this is a false dilemma. “Blind chance” and intelligent design are not mutually exclusive. For example, baseball was designed by an intelligent person (or people), but “blind chance” plays a role in how baseball games turn out. Why can’t this be true of the Universe? There is simply no good reason to believe that an intelligent designer would not construct a Universe that’s based in part on probabilities. After all, it’s obvious from quantum physics that probabilities do play a role in how the Universe works.
On the other hand, there really is no “blind chance” in the Universe, as that term is usually understood by proponents of this argument. The Universe works according to precise rules of physics and chemistry. While there is a probabilistic nature to many things, this is not nearly the same thing as “blind chance.” If the Universe really worked according to “blind chance,” it would be impossible to predict even the probabilities of certain outcomes in nature. But we can make these predictions, and verify them. The Universe does not work by “blind chance.”
Statement 3 has so many problems that the Argument from Design simply falls apart. There are other versions of this argument, but this one, the most popular and well-known, is fatally flawed.
An ontological argument is based on the concept of God. Whereas cosmological arguments and teleological arguments are based on what we observe in nature, ontological arguments are exercises in pure logic. Some people find them irritating and confusing. Others find them endlessly fascinating. The most famous ontological argument is Anselm’s Ontological Argument.
Anselm’s Ontological Argument
- It is greater for a thing to exist in reality than to exist only in the mind.
- “God” means “greatest conceivable being.”
- Suppose God exists only in the mind, and not in reality.
- Then a greater God could be conceived: call this being God*. God* exists both in the mind and in reality.
- But God* is impossible, because God* would be greater than God (statement 1), which was defined as the “greatest conceivable being.”
- Therefore, statement 3 is absurd, since it generated the impossibility in statement 4.
- Therefore, statement 3 is wrong, and God exists both in reality and in the mind.
Anselm’s Ontological Argument is called a reduction to absurdity. The entire point of the argument is to show that statement 3 is absurd. Therefore, its opposite is true: God exists not only in the mind, but in reality. (A few brave critics will suggest that the true opposite of statement 3 is that God does not exist in the mind! But it’s very difficult to defend such an extreme position.)
All of the serious criticism of this argument is focused on statement 1, “It is better for a thing to exist in reality than to exist only in the mind.” Is this a true statement? It depends on what you mean by “greater.”
Anselm had in mind a particular meaning of “greater,” which is clarified when we analyze what he meant by statement 2. God is a being with certain qualities that surpass any quality possessed by any other creature, such as omniscience, omnipotence, moral perfection, etc. As you learn about these qualities, your concept of God grows, and you admire him more and more. But an atheist can have the very same concept of God as the believer, and admire this concept as much as the believer. To say God exists doesn’t change the basic concept held in the mind of the believer or the atheist—even if the atheist accepts statement 4 for the sake of the argument, his conception of God hasn’t really grown by adding existence to all the other qualities that make God God. Thus, existence is not a quality that adds to the concept of God. It’s merely the condition that a God possessing all those wonderful qualities really does exist.
But Anselm’s argument treats existence as though it were a quality like omniscience, omnipotence, moral perfection, etc., that adds to the concept of God and makes the concept greater. It doesn’t. Therefore, statement 1, as Anselm understood it, is simply false. There are several other versions of this argument that attempt to fix Anselm’s mistake.
A psychological argument is based on the human condition, particularly our needs and desires. A fundamental assumption is that real needs are matched to real objects. The most famous psychological argument is the Argument from Desire.
The Argument from Desire
- Every natural, innate desire in us corresponds to some real object that can satisfy that desire.
- But there exists in us a desire which nothing in the Universe can satisfy.
- Therefore, there must exist something outside the Universe which can satisfy this desire.
Statement 1 distinguishes between innate desires and artificial desires. Innate desires are based on our nature. Examples include food, water, sex, and friendship. Artificial desires are conditioned by society. Examples include physical beauty, money, and political power. Statement 2 refers to what is often called the “God-shaped hole” in our souls.
Both premises are criticized. Statement 1 makes a bold assertion, “every natural, innate desire in us corresponds to some real object that can satisfy that desire.” But we can’t be certain this statement is true. Perhaps there are some innate desires that have no corresponding real object. There is no logical reason to simply accept this statement.
Many critics believe that statement 1 implicitly assumes the very thing the argument is trying to prove: that a particular object (God) exists to satisfy a particular innate need-since all innate needs have real objects to satisfy them. If this criticism is valid, then this form of the argument is circular.
Statement 2 is also problematic. First, it asserts a particular innate desire common to all human beings, often called the “God-shaped hole.” We cannot be certain such a desire really exists in all human beings. Second, it asserts nothing in the universe can satisfy this desire. We cannot be certain of this. Assuming this desire does exist in all people, or even in many people, the universe is a big place. Perhaps we just haven’t found the real object that satisfies this desire.
This form of the Argument from Desire has too many problems. But it is possible to rework it into a very strong inductive argument:
- As far as we know, there is no innate desire for a nonexistent object.
- We all have an innate desire for which it seems God is the only satisfaction.
- If God does not exist, this would be one glaring example of an innate desire that has no real object to satisfy it.
- Therefore, it is very likely that God really does exist.
Statement 2 is vulnerable, but there is evidence to support it. Even the atheist must admit that millions find their religious faith to be deeply satisfying.