Is belief in God rational?

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Does it still make sense to follow Jesus after leaving the message? Should we abandon Christianity? Is atheism the best path to follow?

This article is one in a series of studies on whether it is rational or logical to follow Christ after one has left the message. We address a number of questions which should be examined in determining whether belief in God and in the Christian God, in particular, makes sense. You are currently on the topic that is in bold:

  1. Is belief in God rational?
  2. Is the New Testament historically reliable?


Does God exist?

There are four primary arguments that are used to prove the existence of God. These are:

  1. The cosmological or creation argument;
  2. The teleological or design argument;
  3. The axiological or moral argument; and
  4. The ontological argument or the argument from being.

The Cosmological Argument

Natural theology is the study of God based on what we can know from nature through reason and observation and apart from any special revelation (i.e. the Bible). Natural theology is referred to by Paul in Romans 1: 20 when he states that “God’s invisible qualities — his eternal power and divine nature — have been clearly seen, being understood from what has been made, so that people are without excuse.”[1]

The cosmological argument (which is also referred to as the argument from creation or the argument from first cause) is one of the most powerful arguments from natural theology for the existence of God. It has a number of different forms but it can be stated simply as follows:

1. The universe had a beginning.
2. Anything that has a beginning must have been caused by something else.
3. Therefore, the universe was caused by something else, and this cause was God.[2]

This is stated even more succinctly by William Lane Craig in a syllogism he referred to as the Kalām cosmological argument:

1. Whatever begins to exist has a cause.
2. The universe began to exist.
3. Therefore, the universe has a cause.[3]

The first clause is intuitively correct to most people. It is obvious that things that come into existence would expect to have a cause for that existence. Everything that we interact with in our day to day lives began to exist, and all of those things have a cause. The computer that I use began to exist and its cause was Apple, Inc. The chair that I am sitting on while I am typing this essay began to exist at some time in the past and that cause was the particular furniture manufacturer. We all know from experience that things that begin to exist have a cause for their existence.

While there are philosophical arguments that can be used to justify the second clause, it is clear that empirical evidence and current scientific thought provide support for this as well. The Big Bang theory, which states that the universe had a beginning, places the age of the universe at 13.8 billion years.[4] The prevailing cosmological model for the universe is that it has not always existed but began to exist almost 14 billion years in the past.

The most reasonable cause for the existence of the universe is God. Not surprisingly, many atheists are opposed to the thought of a universe that had a beginning. As a result, theories have been posited that result in a universe that did not begin to exist but are also not at odds with the Big Bang. These would include theories that the universe that cycles through periods of expansion and contraction as well as our universe being part of a giant “multiverse”. However, Audrey Mithani and Alexander Vilenkin at Tufts University in Massachusetts have presented proof that such models are flawed from a mathematical perspective. [5]

We understand that time and space exist within the universe and both came into existence with the Big Bang. As a result, any cause for the existence of the universe must be something that exists outside of time and space. And that has been the view of God in the mainstream Christian tradition — Augustine, Boethius, Anselm, Aquinas, Calvin, Edwards— all have viewed God’s existence as outside time, without a past or future.[6]

From the perspective of the cosmological argument from God, and specifically the God of the Bible as he has been proclaimed for millennia as being beyond space and time, is the most reasonable cause for the existence of the universe.

The Teleological Argument

One of the oldest arguments from natural theology is the teleological argument (also know as the argument from design or the intelligent design argument) which dates to the time of Socrates.[7]

The argument can be summarized as:

1. All designs imply a designer.
2. Design can be observed throughout the world and the universe.
3. Therefore, there must be an intelligent designer of the universe.[8]

From experience, we know that complex systems do not arise by accident. There is a designer behind the car I drive, the computer I am using to write this essay and the house that I live in. When we look at complicated objects that have a specific purpose, the design is critical for the object to function in a way to achieve its specific purpose.

Additionally, the more complicated the design, the more intelligent the designer. While a spider can design a spider web and birds can build a nest, more complex designs imply more intelligent designers. Architects design buildings, engineers design bridges and computer scientists design computer chips.

When we observe the world around us and the universe in which we live, complex objects which have a clear design are all around us. The human brain is acknowledged by many to be the most complex object in the known universe. A single human brain has approximately one hundred billion nerve cells connected together with over a quadrillion (a million billion) connection points. While the Milky Way has about two hundred billion stars spread across a hundred light years, the brains one hundred billion neurons are packed into a space of about one and a half liters.[9] The information storage density of a DNA molecule is such it is estimated that all of the world’s information storage needs could be met with about a kilogram of DNA.[10]

Is all the design we observe in nature accidental?

If there is no intelligent designer, if God is not behind all of the design that we see, we are left with the only alternative being that what we observe is not design but rather the result of chance. There is an old saying that a million monkeys typing on a million typewriters would eventually produce a Shakespearean sonnet. But the likelihood of even one such work of Shakespeare being reproduced by such a random process is one in 10 to the power of 690. To put this number in perspective, there are only 1080 atoms in the entire universe.[11]

The evolution of life into the first single cell organism is explained as a combination of random events over billions of years. However, it is also argued that there has not been enough time passed for random chance to work. Fred Hoyle, a well-known English astronomer, stated that given the geological time span of billions of years, the chances are still only one in 10 to the power of 30,000 that so complex a form as even a one-celled animal would emerge by purely natural forces.[12]

The very conditions that permit life to exist in the universe also have the mark of design on them. This is a subset of the teleological argument and is referred to as the “fine-tuning argument.” According to Stephen Hawking:

The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron. ... The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life.[13]

Acclaimed physicist Roger Penrose of Oxford University has calculated that the odds of the low entropy conditions present in the Big Bang having come about as a result of chance are around one chance in 10 to the power of 10 to the power of 123. This number, 10 to the power ot 10 to the power of 123, is so large that inscribing a zero on every subatomic particle in the entire universe would still be well shy of the number.[14] This is just one of a number of fundamental physical constants in physics any significant variation of which would make life within our universe impossible.

Opponents to the fine-tuning arguments have proposed the multiverse theory as an explanation for the fine tuning which science observes. The multiverse consists of an infinite number of universes, of which our universe is only one. It would be expected that in an infinite number of universes that at least one would have the constants, laws and principles of physics required for life. We just happen to find ourselves in that universe. The problem with the multiverse is that there is no evidence for the existence of even one other universe, let alone an infinite number.[15]

The conclusion reached from the teleological argument, given the facts above, is that there is an intelligent designer of the universe and that designer is God.

The psalmist David reached the same conclusion in Psalm 19:1 when he stated, “The heavens declare the glory of God; the skies proclaim the work of his hands.”[16]


  1. The New International Version, (Grand Rapids, MI: Zondervan, 2011), Romans 1:20.
  2. Norman L. Geisler and Ronald M. Brooks, When Skeptics Ask (Wheaton, IL: Victor Books, 1990), 16.
  3. William Lane Craig, Reasonable Faith: Christian Truth and Apologetics, Rev. ed. (Wheaton, Ill.: Crossway Books, 1994), 92.
  4. "Planck reveals an almost perfect universe",, European Space Agency, 2013-03-21.
  5. “Mathematics of Eternity Prove The Universe Must Have Had A Beginning”, MIT Technology Review, , April 24, 2012
  6. Paul Helm, “The Idea of Inerrancy,” in The Enduring Authority of the Christian Scriptures, ed. D. A. Carson (Grand Rapids, MI; Cambridge, U.K.: William B. Eerdmans Publishing Company, 2016), 912.
  7. Charles Hodge, Systematic Theology, vol. 1 (Oak Harbor, WA: Logos Research Systems, Inc., 1997), 226.
  8. Norman L. Geisler and Ronald M. Brooks, When Skeptics Ask (Wheaton, IL: Victor Books, 1990), 20.
  9. “Brain work”, Alun Anderson, The Economist,, November 17, 2011
  10. “How DNA could store all the world’s data”, Andy Extance, Nature, International weekly journal of science,, August 31, 2016.
  11. “Former leading atheist argues for the existence of God”, Lita Cosner, Creation Ministries International, , obtained August 8, 2017
  12. Norman L. Geisler, “God, Objections to Proofs For,” Baker Encyclopedia of Christian Apologetics, Baker Reference Library (Grand Rapids, MI: Baker Books, 1999), 293.
  13. Stephen Hawking, 1988. A Brief History of Time, Bantam Books, p. 7, 125.
  14. Stanley N. Gundry and Steven B. Cowen, eds., Five Views on Apologetics, Zondervan Counterpoints Collection (Grand Rapids, MI: Zondervan, 2000), 177.
  15. David Wood, “The Explanatory Emptiness of Naturalism,” in True Reason: Confronting the Irrationality of the New Atheism, ed. Tom Gilson and Carson Weitnauer (Grand Rapids, MI: Kregel Publications, 2013), 112.
  16. The New International Version (Grand Rapids, MI: Zondervan, 2011), Psalms 19:1.