bookmark_borderOpening Statement from My Debate with Frank Turek

Although I’ve recently been too busy to spend any time writing original content for this blog, I’ve decided to post my opening statement from my 2016 debate with Frank Turek. Enjoy!


Introduction

Good evening! I’d like to thank Craig Freerksen for organizing this debate. I’d also like to thank Dr. Turek for agreeing to participate. Finally, I’d like to thank all veterans, including my opponent, for defending the right to have a debate like this. Now, speaking of our country, I thought I’d borrow a slogan from the presidential campaign. I’m not selling any hats, but I’m here to “make atheism great again.”

Definitions

In this debate, we’ve been asked to assess what best explains reality: naturalism or theism? Before we can answer that question, we need to have some idea of what we’re talking about, so let me begin by defining some terms.
First, by “naturalism,” I mean the view that the physical exists and, if the mental exists, the physical explains why the mental exists.[1] If naturalism is true, then there are no purely mental beings which can exist apart from a physical body and so there is no God or any person or being much like God.
Second, by “supernaturalism,” I mean the view that the mental exists and, if the physical exists, the mental explains why anything physical exists.[2] If supernaturalism is true, then there is no purely physical matter which can exist without some sort of ultimate mental creator.
Third, “personal supernaturalism” is a type of supernaturalism; it adds on the claims that one or more personal mental entities exist and, if a physical world exists, it or they produced the physical world for a purpose.[3]
Fourth, “theism” is a type of personal supernaturalism; it adds on the claim that there is just one mental entity, God, who is all-powerful, all-knowing, and morally perfect.[4]
Finally, fifth, “otherism” is a catch-all category. It says that both naturalism and supernaturalism are false.[5]
Now the question before us in tonight’s debate is this. What best explains reality: theism or naturalism?
In support of a naturalistic answer to that question, I’m going to defend three basic contentions:
(1) The best explanation is the explanation with the overall greatest balance of intrinsic probability and accuracy;
(2) Naturalism is an intrinsically more probable explanation than theism; and
(3) Naturalism is a more accurate explanation than theism.

First Contention

Let’s look, then, at my first basic contention: the best explanation is the explanation with the overall greatest balance of intrinsic probability and accuracy.
By “intrinsic probability” of a hypothesis, I mean the probability independent of the evidence we have for or against it. The intrinsic probability of a hypothesis is determined entirely by its modesty and coherence.[6]
By “accuracy” of a hypothesis, I mean the degree to which a hypothesis’s predictions correspond to reality. We measure accuracy by looking at “evidence.”
By “evidence” I mean something which makes something else more probable than it would have been otherwise. Let me give you an example.[7] Imagine you have two jars of red and blue jellybeans. In the first jar, 90% of the jellybeans are blue and the rest are red. In the second jar, 90% of the jellybeans are red and the rest are blue.
Now imagine you are handed a jelly bean from one of the jars, but you don’t know which jar it came from. If it’s a blue bean, that’s evidence it came from the first jar, not the second. The blue bean doesn’t disprove that it came from the second jar because the second jar also has blue beans, but it’s more likely that it came from the first because there are more blue jellybeans in the first than in the second. Similarly, if it’s a red bean, that’s evidence it came from the second jar. The red bean doesn’t disprove that it came from from the first jar because the first jar also has red beans, but it’s more likely that it came from the second because it has many more red beans.
Mathematicians have a formula called Bayes’ Theorem, which can be used to specify the relationship between intrinsic probability, accuracy, and the overall or final probability of a hypothesis. It follows from Bayes’ Theorem that a hypothesis is probably true, just in case it has a greater overall balance of intrinsic probability and explanatory power than do its alternatives collectively.

Second Contention

Let’s look, then, at my second basic contention: naturalism is an intrinsically more probable explanation than theism.
Intrinsic probability is determined by modesty, coherence, and nothing else. By “modesty,” I mean a measure of how much the hypothesis asserts.[8] The more a hypothesis claims, the more ways there are for it to be false and so, before we start looking at evidence, the less likely it is to be true.
By “coherence,” I mean a measure of how well the parts of a hypothesis fit together.[9] If the different parts count against each other, the hypothesis is less coherent and less likely to be true.
Now consider naturalism and supernaturalism. They are symmetrical claims: naturalism claims that the physical explains the mental, while supernaturalism claims that the mental explains the physical. Both claims are equally modest and equally coherent. Before examining the evidence, both positions are equally likely to be true.[10]
With these definitions in mind, then, I can now defend my second contention. Theism is a type of supernaturalism but could be false even if supernaturalism is true. Furthermore, theism is less modest than either supernaturalism or naturalism. Therefore, before we look at evidence, it is less likely to be true than supernaturalism or naturalism.[11] But that entails that naturalism is intrinsically more probable than theism.

Third Contention

Finally, let’s move onto my third contention: naturalism is a more accurate explanation than theism for many facts.
I’d like to present seven lines of evidence that are red jellybeans, i.e., things more probable on naturalism than on theism.[12]

Physical Matter

(1) Naturalism is the best explanation for the fact that physical reality exists.[13]
If naturalism is true, then physical reality must exist. That’s just part of what naturalism means.
If theism is true, however, things look quite different. The existence of physical reality doesn’t disprove theism; if God exists, God could have created physical space, matter, and energy as part of a plan to create a universe for human beings. But God could have also chosen to create other minds without physical bodies, such as angels. Or God could have chosen to create nothing at all. In other words, God’s existence doesn’t require a physical reality.
So because the physical has to exist on naturalism but does not have to exist on theism, it follows that the existence of physical reality is evidence favoring naturalism over theism.

Success of Science

(2) Naturalism is the best explanation for the fact that science has been so successful without the supernatural.[14]
Imagine a library that contains textbooks for all of the sciences—such as physics, chemistry, and biology—and summarizes current scientific knowledge. The percentage of such knowledge which makes no appeal to the supernatural is extremely high.
Of course, one hears about specific scientific questions which (allegedly) do not have a plausible naturalistic explanation, such as cosmological fine-tuning, the origin of life, and consciousness. But, even if that is or were true, the history of science contains numerous examples of naturalistic explanations replacing supernatural ones and no examples of the reverse. Indeed, naturalistic explanations have been so successful that even most theists concede that supernatural explanations are, in general, unlikely to be true.
Such explanatory success is just what we would expect on naturalism–which entails that all supernatural explanations are false–than it is on theism.[15] And that’s my second line of evidence against theism.

Biological Evolution

(3) Naturalism is the best explanation for the fact that complex life  evolved from simple life.[16]
I’m going to list five scientific facts which support biological evolution. Since Dr. Turek likes acronyms, I’m going to give you the evidence in an acronym, BONES.

  • B is for biogeography;
  • O is for vestigial organs;
  • N is for natural selection;
  • E is for embryology; and
  • S is for stratified fossil record.

Let’s look very briefly at each of these.

Biogeography

First, the evidence indicates that the habitats of plants and animals are distributed in a puzzling way. For example, why are there no land-based mammals on any island more than 300 miles away from the mainland? As University of Chicago biologist Jerry Coyne puts it, “The biogeographic evidence for evolution is now so powerful that I have never seen a creationist book, article, or lecture that has tried to refute it.”[17]

Vestigial Organs

Secondly, a variety of animals have organs which display traits that would be unnecessary if the organs had been designed from scratch, but would have been useful to an ancestor.

Natural Selection

Thirdly, when the genetic differences between living things provides an advantage, things with that advantage tend to be more successful at survival and reproduction than things without that advantage. This is the essence of the process Darwin called natural selection.

Embryology

Fourthly, as Coyne points out, the evidence indicates that all vertebrate embryos begin development in the same way, looking like embryonic fish, but as they progress, they often go through strange contortions before reaching their final form.[18]

Stratified Fossil Record

Fifthly, the available fossil evidence indicates that as one goes from the oldest to the youngest layers of the fossil record, the layers show gradual change from simple to more complex life forms.
Taken together, the BONES evidence is much more probable on biological evolution (which says that complex life evolved from simple life through trans-generational genetic change)[19] than it is on special creationism (which says that God created all life virtually simultaneously).[20]
If either naturalism or supernaturalism is true, life could exist or not exist. If naturalism is true and life exists, evolution pretty much has to be true. But if theism is true, God didn’t have to use evolution. Furthermore, since theism says that at least one mind existed before any physical matter, it gives a reason to expect that any other minds are fundamentally nonphysical. But that, in turn, leads us to predict conscious life was created independently of nonconscious life, contrary to what evolution claims.[21] So theism predicts that evolution is false.
Thus, the scientific fact of evolution is more likely on naturalism than on theism, and so that’s my third line of evidence against theism.

Pain and Pleasure

(4) Naturalism is the best explanation for the biological role (and moral randomness) of pain and pleasure.[22]
I’m going to give three lines of evidence.
First, moral agents experiencing biologically useful pain and pleasure.
Suppose you are a teenager sleeping in a hotel that has caught on fire. The hotel is old and doesn’t have smoke alarms. The fire gets closer and closer to you until you are actually in pain from the smoke and the intense heat. Your pain wakes you up in time for you to escape; you survive and start a family in your twenties. Your pain in this case was biologically useful because it contributed to your survival. This is just what we would expect on naturalism (and human beings are the products of evolution by natural selection).
Second, moral patients experiencing biologically useful pain and pleasure.
Most human beings are moral agents, people who can be held responsible for their actions and their consequences. But some human beings, such as young children and humans with certain mental disabilities, as well as non-human sentient animals, such as primates and dolphins, are moral patients: sentient beings who can be harmed from their own point of view, but are not responsible for their actions.
On naturalism, we would expect that (biological) sentient beings, including moral patients, would experience pain and pleasure because moral patients are biologically similar to moral agents. On theism, however, we would predict that moral patients do not suffer the same kind of pain as moral agents because such pain plays no known moral role in the lives of the moral patients who experience it.
Third, sentient beings experiencing gratuitous pain and pleasure.
Consider, for example, an animal trapped in a forest fire, suffering horrific pain as it slowly burned to death. On the one hand, this kind of pain is biologically appropriate: it is biologically useful that animals in general feel pain when they come in contact with fire. But, on the other hand, this specific instance of pain was not biologically useful because it did not contribute to the biological goals of survival or reproduction.
On naturalism, this is just what we would expect.  If naturalism is true, all animals are the byproducts of unguided evolution by natural selection, which is both indifferent to suffering and incapable of preventing it.
But if theism is true, God could “fine tune” animals so that they only experience physical pain and pleasure when it was morally necessary. So theism leads us to expect that pain and pleasure are fundamentally moral phenomena, which just happens to be connected to the biological goals of survival and reproduction. That’s a huge coincidence that naturalism doesn’t need.
So this evidence is very much more probable on naturalism than on theism.

Mind-Brain Dependence

(5) Naturalism is the best explanation for the fact that human minds are dependent upon the physical brain.[23]
Philosopher Paul Draper of Purdue University puts it this way: “Consciousness and personality are highly dependent on the brain. Nothing mental happens without something physical happening.”[24] Now Michael Tooley, a philosopher at the University of Colorado at Boulder, has stated five lines of evidence in support of this claim.[25]

  • When an individual’s brain is directly stimulated and put into a certain physical state, this causes the person to have a corresponding experience.
  • Certain injuries to the brain make it impossible for a person to have any mental states at all.
  • Other injuries to the brain destroy various mental capacities. Which capacity is destroyed is tied directly to the particular region of the brain that was damaged.
  • When we examine the mental capacities of animals, they become more complex as their brains become more complex.
  • Within any given species, the development of mental capacities is correlated with the development of neurons in the brain.

Take together, this evidence is much more probable on physicalism, which says that the mind is made only of physical matter, than it is on dualism, which says says that the mind is made of two substances (the physical and the mental). if God exists, God is not in any sense dependent on physical arrangements of matter. So theism entails the existence of at least one unembodied mind. Furthermore, if God wanted to create other minds, he didn’t need them dependent on physical brains.
So the dependence of human minds on brains is evidence against the existence of any being who is supposed to have an unembodied mind, including God. Therefore, the physical nature of minds is evidence favoring naturalism over theism.

Empathy and Apathy

(6) Naturalism is the best explanation for the neurological basis of empathy and apathy, including some moral handicaps.[26]
In many cases, our ability to choose do morally good actions depends upon our having properly functioning emotional capacities, especially empathy, i.e., our ability to identify what someone else is thinking or feeling and to respond to their thoughts and feelings with an appropriate emotion.[27]
We now know, thanks to the relatively new discipline of neuroscience, that certain brain abnormalities cause people to experience less or even no empathy.[28] According to Simon Baron-Cohen of Cambridge University, “There is a consensus in neuroscience that at least ten interconnected brain regions are involved in empathy.”[29] These regions are shown on the slide.
For example, violent psychopaths may know in some abstract sense that their behavior is morally wrong, but utterly lack empathy.[30]
While theism is compatible with a neurological basis for moral handicaps, the fact that at least some moral handicaps can be explained neurologically is much more probable on naturalism than on theism. If theism is true, then that means both 

(a) God creates some human beings with moral handicaps that are not the result of the freely chosen actions of any human being;

and

(b) These moral handicaps make it more likely that they will harm others.

What moral justification would God have for allowing both (a) and (b) to obtain? This seems utterly surprising and completely random from a theistic, moral point of view, but precisely what we would expect on naturalism (and blind nature is indifferent to the moral consequences of brain abnormalities).[31]

Nonresistant Nonbelief

(7) Naturalism is the best explanation for nonresistant nonbelief (in God).[32]
Imagine you’re growing up in an orphanage and I told you I had met a man who claims to be your father and who really wants a relationship with you. Days, weeks, even months go by but you never actually meet your father. You never get a card, letter, phone call. In fact, the only evidence that your father is alive is my claim that he exists. Why haven’t you heard from him? Perhaps your father is ashamed for abandoning you. Or maybe he’s a prisoner of war and his captors won’t even let him write you. Although you hope your father is alive and wants to meet you, you remain skeptical.
Just as you do not believe your father is alive and wants to meet you, there are people who do not believe that God exists.[33] But notice that, whatever reasons we might invent to explain your earthly father’s absence do not explain their heavenly father’s absence.
At least some of the people who deny God’s existence are “nonresistant” nonbelievers. As philosopher John Schellenberg explains, their nonbelief is “not in any way the result of their own emotional or behavioral opposition towards God or relationship with God or any of the apparent implications of such a relationship.”[34] Such nonbelievers are open to having a relationship with God—in fact, they may even want it—but are unable to have such a relationship. But why, if God exists, does that happen?
On naturalism, blind nature doesn’t care whether anyone believes in God and so the fact of nonresistant nonbelievers is hardly surprising. On theism, however, this fact is very surprising. On theism, we would expect a perfectly loving God to always make a meaningful relationship available to those He loves.

Conclusion

So, in sum, we’ve seen seven lines of evidence that naturalism is true. I also happen to think there is some evidence for theism, but that it is outweighed by the evidence for naturalism.[35] In my other speeches, I will explain why I think this as I respond to Dr. Turek’s arguments.[36]

Notes

[1] I owe this definition to Paul Draper.
[2] I owe this definition to Paul Draper.
[3] This definition is similar to, but not identical with, one offered by Paul Draper.
[4] I owe this definition to Paul Draper.
[5] I owe this definition to Paul Draper.
[6] I owe this to Paul Draper.
[7] I owe this jelly bean analogy to Paul Draper. Draper’s full analogy also includes an equal number of yellow jelly beans in both jars, where yellow signifies something that is equally likely to have come from either jar and hence is not evidence that it came from either jar. I have omitted the yellow jelly beans solely in the interest of time.
[8] I owe this definition to Paul Draper.
[9] I owe this definition to Paul Draper.
[10] Paul Draper, “God and the Burden of Proof,” Secular Outpost (July 21, 2014), https://secularoutpost.infidels.org/2014/07/21/new-by-paul-draper-god-and-the-burden-of-proof/
[11] Paul Draper, “More Pain and Pleasure: A Reply to Otte” in Christian Faith and the Problem of Evil (ed. Peter van Inwagen, Eerdmans, 2004), 41-54 at 49.
[12] Let N stand for naturalism, T for theism, and F for any of these facts. Using the symbol “Pr(F | H)” to stand for the epistemic probability that F is true conditional upon H, then the claim that some fact is evidence favoring naturalism over theism should be understood as the claim that Pr(F | N) > Pr(F | T).
[13] Jeffery Jay Lowder, “Potential Objections to Swinburne’s Cosmological Argument,” The Secular Outpost (March 17, 2014), https://secularoutpost.infidels.org/2014/03/17/potential-objections-to-swinburnes-cosmological-argument/. Note that here I am using the word “matter” as a way to provide a concrete example of something “physical.”
[14] See Keith M. Parsons, Science, Confirmation, and the Theistic Hypothesis (Ph.D. Dissertation, Kingston, Ontario, Canada: Queen’s University, 1986), 46; Paul Draper, “Evolution and the Problem of Evil” in Philosophy of Religion: An Anthology (3rd ed., ed. Louis Pojman, Wadsworth, 1997), 223-24; and idem, “God, Science, and Naturalism” Oxford Handbook of Philosophy of Religion (ed. William Wainwright, Oxford: Oxford University Press, 2004), 272-303; and Barbara Forrest, “Methodological Naturalism and Philosophical Naturalism: Clarifying the Connection” Philo 3 (2000): 7-29.
[15] Draper 2004.
[16] See Paul Draper, “Evolution and the Problem of Evil” in Philosophy of Religion: An Anthology (3rd ed., ed. Louis Pojman, Wadsworth, 1997), 219-230; cf. Louis P. Pojman, Philosophy of Religion (Mayfield, 2001), chapter 6.
[17] Jerry Coyne, Why Evolution is True (New York: Penguin, 2009), 88.
[18] Coyne 2009, 56.
[19] Draper 1997, 221.
[20] I’m using “virtually simultaneously” as a shorthand way of accounting for the seven literal days described in Genesis 1, in order to contrast that chronology with the sort of geological timescales needed for evolution.
[21] Draper 1997, 224.
[22] Paul Draper, “Pain and Pleasure: An Evidential Problem for Theists.” Nous 23 (June, 1989), 331-350.
[23] Jeffery Jay Lowder, “The Evidential Argument from Physical Minds,” The Secular Outpost (https://secularoutpost.infidels.org/2012/06/13/the-evidential-argument-from-physical-minds-apm/), June 13, 2012.
[24] Paul Draper, “Opening Statement” in William Lane Craig and Paul Draper, Does God Exist? (videotape, West Point, NY, 1996).
[25] Michael Tooley, “Dr. Tooley’s Opening Arguments”  in William Lane Craig and Michael Tooley, The Craig-Tooley Debate: Does God Exist? (http://www.leaderu.com/offices/billcraig/docs/craig-tooley2.html), 1994, spotted 25 Jan 99.
[26] Jeffery Jay Lowder, “The Evidential Argument from Physical Minds,” The Secular Outpost (https://secularoutpost.infidels.org/2012/06/13/the-evidential-argument-from-physical-minds-apm/), June 13, 2012.
[27] Simon Baron-Cohen, The Science of Evil: On Empathy and the Origins of Cruelty (New York: Basic Books, 2012), 16.
[28] Baron-Cohen 2012, 39.
[29] Baron-Cohen 2012, 28.
[30] As Baron-Cohen points out, the neurological basis for moral handicaps challenges traditional views about moral responsibility. “If zero degrees of empathy is really a form of neurological disability, to what extent can such an individual who commits a crime be held responsible for what they have done? This gets tangled up with the free will debate, for if zero degrees of empathy leaves an individual to some extent “blind” to the impact of their actions on others’ feelings, then surely they deserve our sympathy rather than punishment.” See Baron-Cohen 2012, 160.
[31] Some theists have pointed out that moral evil, such as fallen angels or demons choosing to do evil, might explain so-called “natural evils.” This argument makes the inverse point: certain natural evils explain at least some moral evil.
[32] J.L. Schellenberg, Divine Hiddenness and Human Reason (Ithaca: Cornell University Press, 1993); idem, 2007.
[33] This sentence, of course, assumes that at least some (if not most) professions of atheism are genuine. Those familiar with intra-Christian debates on apologetic methodologies will notice that I have just ruled out the claim of some (or all?) presuppositionalists, namely, that there are no atheists and instead there are only professed atheists. I agree with  John Schellenberg: “it would take something like willful blindness to fail to affirm that not all nonbelief is the product of willful blindness (even if some of it is).” See J.L. Schellenberg, “What Divine Hiddenness Reveals, or How Weak Theistic Evidence is Strong Atheistic Proof” God or Blind Nature? Philosophers Debate the Evidence (http://infidels.org/library/modern/john_schellenberg/hidden.html), 2008.
[34] Schellenberg 2008.
[35] It follows from a Bayesian approach to evidence sketched in my first contention that there can be “true evidence” for a false proposition. Consider, for example, people convicted on the basis of eyewitness testimony for crimes they didn’t commit, only to be exonerated years or decades later by DNA evidence. The eyewitness testimony was some evidence for a false proposition (“The defendant is guilty”), but it was greatly outweighed by the DNA evidence against that false proposition. The fact that there can be true evidence for false propositions should serve as a “warning flag” to anyone who wants to claim that there is absolutely no evidence for naturalism (or theism). “There is no evidence for naturalism (or theism)” does not follow from “Naturalism (or theism) is false” or even “I believe naturalism (or theism) is false.”
[36] I am grateful to Paul Draper, John Danaher, Robert Greg Cavin, and Eddie Tabash for helpful comments on a previous version of this speech.

bookmark_borderLink: Matthew Ferguson on “Understanding the Spirit vs. the Letter of Probability”

A while back, I wrote a brief commentary on William Lane Craig’s critique of Bart Ehrman on the probability of miracles. Matthew Ferguson recently weighed in. He agrees with my conclusions, but greatly amplified them by writing an entire essay expounding on supporting points. I highly recommend his essay to anyone interested in the topic of the probability of miracles in general and the probability of Jesus’ alleged resurrection in particular.

bookmark_borderRepost: Extraordinary Claims Require Extraordinary Evidence (ECREE), Part 2: Is ECREE False? A Reply to William Lane Craig

(This article was originally published on this blog on June 21, 2012. I am reposting because William Lane Craig recently tweeted a link to a video in which he objects to ECREE.)
In my last post, I offered a Bayesian interpretation of the principle, “extraordinary claims require extraordinary evidence” (ECREE). William Lane Craig, however, disagrees with ECREE. In a response to philosopher Stephen Law, Craig wrote this.

This sounds so commonsensical, doesn’t it? But in fact it is demonstrably false. Probability theorists studying what sort of evidence it would take to establish a highly improbable event came to realize that if you just weigh the improbability of the event against the reliability of the testimony, we’d have to be sceptical of many commonly accepted claims. Rather what’s crucial is the probability that we should have the evidence we do if the extraordinary event had not occurred.3 This can easily offset any improbability of the event itself. In the case of the resurrection of Jesus, for example, this means that we must also ask, “What is the probability of the facts of the empty tomb, the post-mortem appearances, and the origin of the disciples’ belief in Jesus’ resurrection, if the resurrection had not occurred?” It is highly, highly, highly, improbable that we should have that evidence if the resurrection had not occurred.
————
[3] See the very nice account by S. L. Zabell, “The Probabilistic Analysis of Testimony,” Journal of Statistical Planning and Inference 20 (1988): 327-54.

I agree with Craig that it would be incorrect to “just weigh the improbability of the event against the reliability of the testimony.” I also agree with Craig that “the probability that we should have the evidence we do if the extraordinary event had not occurred … can easily offset any improbability of the event itself.” I disagree with Craig, however, regarding his interpretation that ECREE requires that we ignore that probability. This can be seen using Bayes’s Theorem (BT).
Let B represent our background information; E represent our evidence to be explained; H be an explanatory hypothesis, and ~H be the falsity of H. Here is one form of BT:
BT
As I argued in my last post, an “extraordinary claim” is an explanatory hypothesis which is extremely improbable, conditional upon background information alone, i.e., Pr(H | B) <<<  0.5. And “extraordinary evidence” can be interpreted as the requirement that a hypothesis’s explanatory power is proportionally high enough to offset its prior improbability (the “extraordinary claim”). Here I offer an even more precise definition.
It follows from BT that H will have a high epistemic probability on the evidence B and E:
BT2just in case it has a greater overall balance of prior probability and explanatory power than its denial:
BT3Thus, we can somewhat abstractly define “extraordinary evidence” as evidence that makes the following inequality true:
BT4With that inequality in mind, let’s return to Craig’s objection to ECREE. Here again is the relevant portion of his objection:

Probability theorists studying what sort of evidence it would take to establish a highly improbable event came to realize that if you just weigh the improbability of the event against the reliability of the testimony, we’d have to be sceptical of many commonly accepted claims. Rather what’s crucial is the probability that we should have the evidence we do if the extraordinary event had not occurred.

It seems, then, that Craig’s objection to ECREE is based upon an interpretation of ECREE which requires that we only consider the “extraordinary claim,” i.e., Pr(H | B). If that interpretation is correct, then I will join Craig in rejecting ECREE. But is it correct?
In mathematical notation, “the probability that we should have the evidence we do if the extraordinary event had not occurred” is Pr(E | B & ~H). But now consider again the inequality used to define extraordinary evidence.
BT4
The expression, Pr(E | B & ~H), is literally right there, in the numerator on the right-hand side. It appears, then, that Craig’s objection is based upon a misinterpretation of ECREE. For the same reason, Craig’s reason that ECREE would cause us “to be sceptical of many commonly accepted claims” is therefore misplaced.
I could be wrong, but I suspect there are two factors which contributed to this misinterpretation. First, many skeptics have used ECREE in connection with (or as support for) Hume’s argument against miracles. While I’m inclined to agree with John Earman that Hume’s argument is highly overrated–i.e., it may be the case that BT does not provide Hume with the support many skeptics think it provides–this is not of obvious relevance to ECREE. ECREE, like BT, is not dependent on Hume.
The other factor which may have contributed to the misinterpretation is the definition of “extraordinary claim;” Craig may disagree with the criteria skeptics have used to determine whether a claim is extraordinary. I think it is helpful to use probabilistic notation to clarify the issue. Again, I proposed that an “extraordinary claim” is an explanatory hypothesis which is extremely improbable, conditional upon background information alone, i.e., Pr(H | B) <<<  0.5. Let’s assume, for the sake of argument, that definition is wrong. Instead, define an “extraordinary claim” as any explanatory hypothesis H which has a prior probability below some number x, i..e., Pr(H | B) < x, where x can be any real number between 0 and 1. Here’s the point. X can be any real number between 0 and 1. It doesn’t matter which value one chooses, since BT can accommodate all probability values. In terms of calculating the final probability of H, Pr(H | E & B), we use the same formula–BT–regardless of whether H is an extraordinary claim. From a mathematical perspective, it makes no difference whatsoever whether we label a claim “extraordinary” or “ordinary.” We can use BT to assess the epistemic probabilities of both types of claims.

bookmark_borderGeisler & Turek Rebuttal: Chapter 9 (Part 2)

Chapter 9. Do We Have Early Eyewitness Testimony about Jesus?

By Matthew Wade Ferguson and Jeffery Jay Lowder
(This post continues where part 1 left off.)
(ii) New Testament Textual Accuracy: “Textual accuracy” measures the degree to which copies of a document match that of the original document. Although none of the original New Testament documents have survived, Geisler and Turek argue that the textual accuracy of the New Testament documents is superior to that of other ancient documents. In their words:

In fact, the New Testament documents have more manuscripts, earlier manuscripts, and more abundantly supported manuscripts than the best ten pieces of classical literature combined. (225)

We agree with Geisler and Turek. If someone were to fallaciously claim that the New Testament can’t be trusted, as a whole, because it has been textually corrupted, then Geisler and Turek would be correct to object that this is false, because we have (mostly) reliable manuscripts.
By the same token, however, the New Testament’s textual accuracy does not improve its historical accuracy. Accurate textual transmission can preserve the historical accuracy of a work that was originally historically reliable, but it can do nothing to improve or save the historical accuracy of a work that was originally based on ahistorical legends. With that in mind, let us turn now to the question of historical accuracy.
(iii) New Testament Historical Accuracy: In this section, Geisler and Turek attempt to do three things: (a) propose seven historical criteria or tests to “determine whether or not to believe a given historical document” (230); (b) refute common objections to the reliability of the New Testament; and (c) argue that the NT documents are early.
Regarding (a) the historical tests, Geisler and Turek list the following seven tests: (1) do we have early testimony; (2) eyewitness testimony; (3) multiple, independent eyewitness sources; (4) trustworthiness; (5) corroborating evidence from archaeology or other writers; (6) enemy attestation; and (7) embarrassing details. According to them, “documents that meet most or all of these historical tests are considered trustworthy beyond a reasonable doubt” (231).
Let’s “zoom out” for a moment from the topic of the NT’s historical reliability and instead look at how this argument fits into Geisler’s and Turek’s “Twelve Points that Show Christianity Is True.” Geisler and Turek seek to defend the following inference:

6. The New Testament is historically reliable.
7. The New Testament says Jesus claimed to be God.
8. Jesus’ claim to be God was miraculously confirmed by
a. His fulfillment of many prophecies about himself;
b. His sinless life and miraculous deeds;
c. His prediction and accomplishment of his resurrection.  (28)

Geisler’s and Turek’s statement about historical tests, as well as points 6-8 of their twelve-point case for Christianity, suggests a previously unnamed version of an existing inductive argument form, which we shall call the “argument from general reliability.” Before we can introduce that argument form, however, we first need to review its “parent” argument known, the statistical syllogism. Statistical syllogisms have the following logical structure or form.

(1) Z percent of F are G.
(2) x is F.


(3) [Z% probable] Therefore, x is G.

One “child” version of the statistical syllogism is the argument from authority, which we discussed in chapter six. The simple version of the argument from general reliability is another “child” version of the statistical syllogism. It has the following structure.

(4) Source S is generally reliable.
(5) S reports that event E occurred.


(6) [probable] E occurred.

With this schema in place, let’s return to Geisler’s and Turek’s statement, “documents that meet most or all of these historical tests are considered trustworthy beyond a reasonable doubt.” If we replace S with “The New Testament documents” and E with “E1, …, En” (to represent the events reported by the New Testament documents), then Geisler’s and Turek’s simple argument from general historical reliability may be summarized as follows.

(4’) The New Testament documents are generally historically reliable.
(5’) The New Testament documents report that E1, …, En occurred.


(6’) [probable] E1, …, En occurred.

What Geisler and Turek fail to realize, however, is that general historical reliability alone does not suffice to make it probable, much less probable “beyond a reasonable doubt,” that event E1, …, En occurred. Although simple arguments from reliability are statistical syllogisms, simple arguments from reliability are logically incorrect because they violate the inductive Total Evidence Requirement. Such arguments ignore information about the base rates of events like E1, …, En and instead consider only information about the reliability of the historical source which reports E1, …, En. Statisticians call this error the base rate fallacy.
In order to fully appreciate the force of this objection, let’s turn to a non-theological example, one which is actually quite famous in the academic literature about reasoning under uncertainty. Amos Tversky and Daniel Kahnemann, the authors of this example, describe it as follows.[1]

A cab was involved in a hit-and-run accident at night. Two cab companies, the Green and the Blue, operate in the city. You are given the following data:
(a) 85% of the cabs in the city are Green and 15% are Blue.
(b) A witness identified the cab as Blue. The court tested the reliability of the witness under the same circumstances that existed on the night of the accident and concluded that the witness correctly identified each one of the two colors 80% of the time and failed 20% of the time.
What is the probability that the cab involved in the accident was Blue rather than Green?

If you answered “There is an 80% probability the cab was blue,” you are in good company. Most people who consider this example say that the answer is “blue” because they are impressed by the witness’s 80% reliability. They seem to be implicitly appealing to the following simple version of the argument from general reliability.

(7) 80% of cab identifications made by witness W under conditions similar to those at the time of the hit-and-run accident are correct.
(8) W’s identification of the cab involved in the hit-and-run accident as a blue cab is a cab identification made by W under similar conditions.


(9) [80% probable] W’s identification of the cab involved in the hit-and-run accident as a blue cab is correct, i.e., a blue cab was involved in the hit-and-run accident.

The correct answer, however, is “There is a 59% probability the cab was green.” The argument in (7)-(9) is logically incorrect because its reference class (“cab identifications made by witness W under conditions similar to those at the time of the hit-and-run accident”) violates the requirement of total evidence. It does this by ignoring what we know about the base rates of green and blue cabs, i.e., the proportion of cabs that are green (85%) is much greater than the proportion of cabs that are blue (15%). Therefore, despite W’s 80% reliability, the most likely explanation (probability=59%) is that W is mistaken and he actually saw a green cab.
Still not convinced? Imagine that the town has exactly 1,000 cabs, so that 85%=850 and 15%=150. Then the breakdown in cabs can be shown by the diagram in Figure 2.

figure2

Figure 2

Since W is 80% accurate, when he testifies about the 850 green cabs, he will correctly testify that 80% of those 850 cabs (=680) were green and he will incorrectly testify that 20% of those 850 cabs (=170) were blue. This is shown below in Figure 3.

figure3

Figure 3

Similarly, when W testifies about the 150 blue cabs, he will correctly testify that 80% of those 150 blue cabs (=120) were blue and he will incorrectly testify that 20% of those 150 blue cabs (=30) were green. This is shown in Figure 4.

figure4

Figure 4

Let’s now return to our question: if an 80% reliable witness testifies the cab was blue, is it more likely that the cab was blue or green? The diagram in Figure 4 makes it easy to correctly calculate the probability, without having to remember the probability theorem known as Bayes’s Theorem. If we want to calculate the probability that the cab was blue, we take the number of times W correctly testified that the cab was blue (120) and divide it by the total number of times W testified that the cab was blue (170+120=290). In probability notation:

eq-blue

Similarly, if we want to calculate the probability that the cab was green, we take the number of times W incorrectly testified that the cab was blue (170) and divide it by the total number of times W testified that the cab was blue (170+120=290). In probability notation:

eq-green

Although an 80% reliable witness testified the cab was blue, it is more likely that the cab was green because there are so many more green cabs than blue cabs. Our specific information about W’s reliability has been outweighed by our general information about the base rates of green and blue cabs. In the words of Tversky and Kahnemann, “In spite of the witness’s report, therefore, the hit-and-run cab is more likely to be Green than Blue, because the base rate is more extreme than the witness is credible.”[2]
Thus, instead of the statistical syllogism in (7)-(9), we should instead use a modified version, which we may call the complex version of the argument from general reliability.

(7’) 59% of all blue cab identifications made by W under similar conditions are incorrect.
(8’) W’s identification of the cab involved in the hit-and-run accident as a blue cab is a blue cab identification made by W under similar conditions.
(10) The percentage stated in (7’) correctly incorporates the available information about the base rates of blue cabs.


(9’) [59% probable] W’s identification of the cab involved in the hit-and-run accident as a blue cab is incorrect.

We have shown that simple versions of arguments from reliability to the historicity of an event are logically incorrect by ignoring information about the base rate of events of that type and, consequently, by using a reference class which fails to embody the total available evidence.
This, in turn, entails that Geisler’s and Turek’s twelve-point case for Christianity is, at best, incomplete. In order to show that the New Testament’s historical claims—such as the claim that Jesus was crucified, died, was buried, and so forth—are probably true, Geisler and Turek must do more than defend the general historical reliability of the New Testament. They must also show that this general historical reliability is not outweighed by the base rates of those events.
 


Rebuttal to Geisler’s and Turek’s “I Don’t Have Enough Faith to be an Atheist”
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Notes
[1] Amos Tversky and Daniel Kahnemann, “Evidential Impact of Base Rates,” Judgment under Uncertainty: Heurists and Biases (ed. Daniel Kahnemann, Paul Slovic, and Amos Tversky, New York: Cambridge University Press, 1982), 156-57.
[2] Tversky and Kahnemann 1982, 157.

bookmark_borderYouTube Video of Today’s Miller-Cavin Debate on Jesus’ Resurrection

Here is the link to the YouTube video of today’s debate between Callum Miller and Robert Greg Cavin on the historicity of Jesus’ resurrection.
[youtube]https://www.youtube.com/watch?v=8aBSAw5I7fg[/youtube]
Also, the Secular Outpost YouTube Channel has a playlist for all of Cavin’s debates on Jesus’ resurrection.
[youtube]https://www.youtube.com/playlist?list=PL5QAvmnRlfhZ0kRRwYzvzK0B-OSddaIrH[/youtube]
Related Links:

 

bookmark_borderMatthew Ferguson: History, Probability, and Miracles (2013)

Historian Matthew Ferguson uses Bayes’ Theorem to analyze the historicity of miracle claims. Among other things, Ferguson compares the historical evidence for a purported miracle by Vespasian to the historical evidence for the purported resurrection of Jesus.
LINK
Note: as always, links do not constitute endorsement.

bookmark_borderEvidential Asymmetry, Scientific Confirmation of Prayer, and Horrific Evils

1. The General Case
One of the most important (and equally most often forgotten) lessons that Bayes’s Theorem can teach us about evidence is that the strength of evidence is a ratio. To be precise, let H1 and H2 be rival explanatory hypotheses, B be the relevant background information, and E be the evidence to be explained. Now consider the following ratio:

Pr(E | B & H1)
—————–
Pr(E | B & H2)

If Pr(E | B & H1) > Pr(E | B & H2), then this ratio is greater than one and the evidence favors H1 over H2. If Pr(E | B & H2) < Pr(E | B & H1), then this ratio is less than one and the evidence favors H2 over H1. And if Pr(E | B & H1) = Pr(E | B & H2), then this ratio is equal to one and the evidence favors neither H1 nor H2.
Paul Draper has taught me that this ratio has some interesting implications for topics that come up in debates between theists and naturalists. Suppose that Pr(E | B & H1) is really high and Pr(E | B & H2) is middling. In this case, there will be an evidential asymmetry: if E is true, E is not strong evidence for H1 over H2, but if E is false, then ~E is strong evidence for H2 over H1. This can be shown with a couple of examples.
First, suppose that E is true. If E is true, then E is not strong evidence for H1 over H2. This follows because the ratio of Pr(E | B & H1) to Pr(E | B & H2) is not high.
Second, suppose that E is false. This is where things get interesting. Because Pr(E | B & H1) is really high, the negation of E would strongly favor H2. Again, this follows from the ratio of the likelihoods: the ratio of Pr(~E | B & H1) to Pr(~E | B & H2) is high.
It is mathematically necessary that this evidential asymmetry will always be present when the evidence has a middling probability on one hypothesis and a very high (or very low) probability on the negation of that hypothesis. (The basic idea is that is the range of probabilities is zero to one, a high probability divided by a middle one must be relatively small while a middling probability divided by a low one must be relatively large.)
2. The Efficacy of Prayer and Scientific Confirmation
Let’s assume, as appears to be the case, that recent scientific studies have failed to confirm the efficacy of prayer. If facts about evil and divine hiddenness are included in our background knowledge, then those study results do not strongly favor naturalism over theism because the ratio of the likelihood of the evidence on naturalism to the likelihood of the evidence on theism is not really high. (This follows because the probability of such studies given theism and that background information is middling.) But now imagine the results had turned out differently and the studies had confirmed the efficacy of prayer. In that case, such results would strongly favor theism over naturalism.
This result shows that atheists are making a mistake when they accuse theists of using an unjustified double standard by dismissing the (negative) study results as evidentially insignifcant.  Rather, theists are correct that if the study results had confirmed prayer, then such positive results would have been strong evidence favoring theism over naturalism, but the absence of such results is only weak evidence favoring naturalism over theism.
3. Horrific Evils
The topic of horrific evils provides another example of evidential asymmetry. Horrific evils have a middling probability given naturalism but a very low probability given theism. So if horrific evils were absent, that fact wouldn’t strongly favor theism over naturalism, whereas the presence of horrific evils strongly favors naturalism over theism.
Acknowledgment
I owe the main point of this post, as well as both examples, to Paul Draper. Any errors in this post are, of course, mine.