In March 2008 Dr. Keller presented a "Reasons for God" lecture at many universities, including Berkeley, Georgetown, U of Penn -- even at Google's headquarters. Keller shows remarkable (all too rare!) ability to find the heart of the matter.
The following summarizes his insights.
Everyone who believes or disbelieves in God does so because of three factors:
• intellectual (rational, logical arguments for or against the existence of God);
• personal (experiences and how they are interpreted);
• social (the beliefs of people we need or admire seem more plausible to us than beliefs of people we don't need or admire).
Belief or disbelief should never be reduced to one of these three (eg. "you wouldn't be a Christian if you were born in Madagascar; but I used intellect and logic to arrive at my position.") No, all beliefs, whether secular or religious, have social as well as intellectual roots. All three of these factors play a part in disbelief as well as belief.
Keller uses the image of a ladder with three rungs to organize his presentation of the reasons for God. He envisions persons moving up these rungs as they move from unbelief to belief.
First rung
Persons are standing on the first rung when they realize that it takes just as much faith to disbelieve in God as to believe. Why? According to Keller, the arguments which seek to prove the non-existence of God inevitably fall flat. They cannot disprove God; therefore, disbelief in God is a matter of faith.
One argument for the non-existence of God:
Evil and suffering show that God does not exist (an all-good God would choose to remove all pointless evil and suffering; an all-powerful God would be able to do so; evil exists; therefore the all-good, all-powerful God of the Bible does not exist.)
This argument combines personal and intellectual factors, and has much power.
Philosophers have shown that this argument does not work. How do we know that suffering is pointless? We cannot imagine a good reason for some suffering, but that does not mean there is not a reason. A God who is big enough for us to be mad at for not stopping suffering and evil would also be big enough to have reasons for the suffering that we cannot understand.
Keller quotes William P. Alston (Syracuse University philosophy professor) as saying, "the effort to demonstrate that evil disproves God is now acknowledged on almost all sides in philosophy as completely bankrupt."
Another argument against God's existence:
If there is a God, how can his believers have done so much evil? If a good God exists, then those who claim to follow him wouldn't be so evil. Christianity has produced the Crusades, Islam has produced global terrorism, etc. Religion poisons everything; so let's drop the idea of God.
Czeslaw Milosz (Polish poet) on how atheism can be used for evil:
"Religion used to be the opium of the people. To those suffering humiliation, pain, illness, and serfdom, religion promised the reward of an after life. But now, we are witnessing a transformation, a true opium of the people is the belief in nothingness after death, the huge solace, the huge comfort of thinking that for our betrayals, our greed, our cowardice, our murders, we are not going to be judged." --"Discreet Charm of Nihilism" (The New York Review of Books, November 19, 1998)
This argument doesn't disprove or prove anything. The fruit of violence is grown in the soil of all worldviews. Yes, out of Christianity grew the Crusades and anti-abortion bombers, and out of Islam came global terrorism, and so on. But out of atheism grew Stalin and the Khmer Rouge and others. There is something in the human heart that is so prone to violence and oppression that it can twist any philosophy, worldview, or belief about God into a warrant for violence.
Yet another argument against the existence of God:
Atheists don't have to disprove God; the burden is on believers to prove it -- just as the burden of proof is on believers in the Abominable Snowman, etc. A person is warranted in assuming God does not exist until it is proven otherwise.
Agreed, for objects or things within the universe, there's no reason to believe they exist until they are proven to exist. But a God who created all things would, by definition, be beyond the universe. So this argument fails -- one cannot expect to find "proof" of a such a God (who is transcendent, exists outside of creation) by simply looking in creation.
Another reason this argument falls flat: one's whole life is based on things we cannot empirically prove, such as memory (cannot prove it without using it).
The import of this: if we can't disprove God but nonetheless live as though there is no God, we are taking a big risk.
When one recognizes that it takes as much faith to disbelieve in God as to believe, one is on the first rung.
Second rung
The second rung in the ladder that leads to belief in God is when we see that it takes more faith to disbelieve than to believe.
Keller's first example of how belief in God makes more sense than disbelief is the fine-tuning of the universe.
The most fundamental characteristics and constants of our cosmos (eg. the relative strengths of gravity and the forces that operate inside atomic nuclei, as well as the masses and relative abundances of different particles) are perfectly calibrated to support organic life. This is sometimes called the Anthropic Principle (the universe seems designed to produce humanity).
The odds against those fundamental regularities and constants happening by sheer chance are smaller than one-in-a-trillion.
Francis Collins (interview with Steve Paulson at salon.com):
"When you look from the perspective of a scientist at the universe, it looks as if it knew we were coming. There are 15 constants -- the gravitational constant, various constants about the strong and weak nuclear force, etc. -- that have precise values. If any one of those constants was off by even one part in a million, or in some cases, by one part in a million million, the universe could not have actually come to the point where we see it. Matter would not have been able to coalesce, there would have been no galaxy, stars, planets or people. That's a phenomenally surprising observation. It seems almost impossible that we're here. And that does make you wonder -- gosh, who was setting those constants anyway? Scientists have not been able to figure that out."
Charles Edward White, "God by the Numbers" (http://www.christianitytoday.com/ct/2006/march/26.44.html) excerpt:
"The fine-tuning of the universe is shown in the precise strengths of four basic forces. Gravity is the best known of these forces and is the weakest, with a relative strength of 1. Next comes the weak nuclear force that holds the neutron together. It is 1034 times stronger than gravity but works only at subatomic distances. Electromagnetism is 1,000 times stronger than the weak nuclear force, and the strong nuclear force, which keeps protons together in the nucleus of an atom, is 100 times stronger yet. If even one of these forces had a slightly different strength, the life-sustaining universe we know would be impossible.
If gravity were slightly stronger, all stars would be large, like the ones that produce iron and other heavier elements, but they would burn out too rapidly for the development of life. On the other hand, if gravity were weaker, the stars would endure, but none would produce the heavier elements necessary to form planets.
The weak nuclear force controls the decay of neutrons. If it were stronger, neutrons would decay more rapidly, and there would be nothing in the universe but hydrogen. However, if this force were weaker, all the hydrogen would turn into helium and other elements.
The electromagnetic force binds atoms to one another to form molecules. If it were either weaker or stronger, no chemical bonds would form, so no life could exist.
Finally, the strong nuclear force overcomes the electromagnetic force and allows the atomic nucleus to exist. Like the weak nuclear force, changing it would produce a universe with only hydrogen or with no hydrogen.
In sum, without planets, hydrogen, and chemical bonds, there would be no life as we know it. ...
The second component to be considered when calculating the likelihood of this life-supporting universe is the presence of habitable planets. In addition to the fine-tuning of the whole universe, there needs to be a carefully specified place where life can reside. Life as we know it can only exist within certain limits. There are at least 45 parameters, from the size of our galaxy to the mass of the moon, which permit the presence of life on a planet. A huge galaxy erupts with too many stars and thus disturbs planetary orbits, but a tiny galaxy does not produce enough heavy elements for a planet to form. At the other end of the spectrum, too large a moon destabilizes a planet's orbit, while having no moon or one that is too small permits a planet to wobble as it spins and disrupts the planet's climate.
Atheists are right in pointing out that this fine-tuning argument does not prove that a Creator exists. For instance, maybe at the Big Bang an almost infinite number of parallel universes were created at once and we are in the universe that happens to have everything right.
But consider Alvin Plantinga's illustration of a poker game in which the dealer deals himself twenty straight hands of four aces. As the other players are about to pound him for cheating, the dealer says, "wait, you can't prove I'm cheating; there are a trillion parallel universes and we just happen to be in one where the chances of dealing twenty straight hands of four aces has been realized." He is strictly right -- it is possible that there are trillions of universes and this is the one universe in which all those aces are dealt. But it's a lot more plausible to believe that he is cheating -- the other players will still slug him! No one lives their life the way the dealer suggests. In the same way, the existence of all those fine-tuned constants is strong evidence that God exists.
A second instance of belief in God making more sense of what we see in this world than disbelief is the ideal of human rights, that each human being is of infinite worth.
Alan Dershowitz (Shouting Fire: Civil Liberties in a Turbulent Age (Little, Brown; 2002) writes that there are three possible sources for our conviction concerning human rights:
• God - are humans given intrinsic value and rights because they are created by God in his image? Dershowitz rejects this answer: too many of us don't believe in God, so we need to find another basis for human rights.
• nature - does creation show us that it's natural to honor the individual? Dershowitz again says no -- natural selection and Darwinian principles are all about strong eating the weak, which contradicts everything we believe about human rights.
Annie Dillard in Pilgrim at Tinker Creek (p.178-180) vividly writes about nature brutalizing her feelings of right and wrong:
"I had thought to live by the side of the creek in order to shape my life to its free flow. But I seem to have reached a point where I must draw the line. It looks as though the creek is not buoying me up but dragging me down. Look: Cock Robin may die the most gruesome of slow deaths and nature is no less pleased; the sun comes up, the creek rolls on, the survivors still sing. I cannot feel that way about your death, nor you about mine or either of us about the robin's... We value the individual supremely, and nature values him not a wit. It looks for the moment as though I might have to reject this creek life unless I want to be utterly brutalized. ...
"Either this world, my mother, is a monster or I am a freak.
"Consider the former: the world is a monster. ... There is not a people in the world who behaves as badly as praying mantises. But wait, you say, there's no right or wrong in nature; right and wrong is a human concept. Precisely: we are moral creatures in an amoral world. ...[A] monstrous world running on chance and death, careening blindly from nowhere to nowhere, somehow produced wonderful us. [This world runs on chance and death and power, but I cherish life and the rights of the weak versus the strong.] I crawled out of a sea of amino acids and now I must whirl around and shake my fist at that sea and cry Shame! ... We little blobs of soft tissue crawling around on this one planet's skin are right, and the whole universe is wrong.
"Or consider the alternative. ... Creation itself is [fine, and] it is only human feeling that is freakishly amiss. The frog that the giant water bug sucked had, presumably, a rush of pure feeling for about a second, before its brain turned to broth. I, however, have been sapped by various strong feelings about the incident almost daily for years. ... All right then. It is our emotions [and values] that are amiss. We are freaks, the world is fine, and let us all go have lobotomies to restore us to a natural state. We can leave the library then, go back to the creek lobotomized, and live on its banks as untroubled as any muskrat or reed. You first."
If we claim that evolution-driven, survival-of-the-fittest type of behavior is inappropriate for us, we're appealing to something beyond nature.
• positive law - did we create morality through law, custom, etc. because it makes society work better? Dershowitz says this explanation doesn't work because it has genocide being wrong only because those in power say so. But the whole point of human rights is that it enables us to turn to the majority or the strong and insist that they honor the interests of the individual. A society that can create human rights can also end them, and we instinctively know that is wrong.
So what does Dershowitz suggest as the source of human rights? He says they are just "there" -- we discover them as we reflect on our long experience with wrongs and injustice, we don't create them.
To summarize, without the existence of God, the fine-tuning of the universe and also human rights just "happen" with no explanation. One has reached the second rung in Keller's ladder when one realizes that if God exists, then these things are no longer improbable but probable. (Keller says he could list 20 more such examples.) Again, this is not proof of God. It rather shows two instances of leaps one who disbelieves in God must make -- instances where it takes more faith to disbelieve than it does to believe.
Third rung
This leads to the third rung of the ladder. So far we have not arrived at certainty of the existence of God; at best, we have only high probability. The third rung is when we see that it takes personal commitment to arrive at certainty.
If someone falls off a cliff and on the way down sees a branch strong enough to hold them, they won't be helped if they only note evidence of its sturdiness. They must grab onto it (commit) or they will fall. Even if they have only a small amount of faith in the branch's ability to hold them, if they reach out and grab it, they will be saved. Only then can they move from probability to certainty. Weak faith in a strong object is infinitely better than strong faith in a weak object.
Listen to Dr. Keller's lecture
at U. of Penn. (edited to shorten) - streaming audio | mp3
at Google HQ - streaming audio | mp3