Sunday, February 14, 2016

More on Evidence vs. Faith

Victor Reppert sees the evidence as a relationship between the likelihood of a fact and some postulated state of affairs.  Given the postulated state of affairs Y is true, if a particular fact X is more likely to exist, then X is said to be evidence in favor of Y.  To put it in Victor's own words:
I understand evidence in Bayesian terms. For me, X is evidence for Y just in case X is more likely to exist given Y than given not-Y. By this definition, something can have evidence for it and be false. - Reppert 
In his view, an individual fact is regarded as evidence for or against the postulated state of affairs.  It may then be possible to judge whether that postulation is true, perhaps on the basis of a single fact in evidence, or perhaps by weighing several pieces of evidence for and against the postulation.

In my view, this way of looking at evidence is wrong, and quite likely to result in incorrect conclusions.

Let's take a simple example.  You live in an isolated area in the woods.  The fact in evidence is peanut shells found in your yard.  You postulate a state of affairs thus: birds broke open the peanuts and ate them, leaving the shells in your yard.  Your husband postulates that the squirrels did it.  So we have two competing hypotheses:
H1: Birds ate peanuts and left the shells behind.
H2: Squirrels ate peanuts and left the shells behind.  
We can call the fact in evidence E: Peanut shells were found in the yard.  But using Victor's Bayesian approach to examining the evidence, both H1 and H2 would make E more likely.  That is to say, E is evidence in favor of both H1 and H2.  Where do we go from here?  We probably need to start looking for other pieces of evidence.  If we are an H1 supporter, we will probably look for more evidence in favor of our theory, and likewise if we are an H2 supporter.  In the end, the one who has gathered the most pieces of evidence in favor of his favored theory wins, right?  Wrong.  The true state of affairs is not to be found by taking this approach, as we shall see.

How should one evaluate evidence in a manner that is most likely to reach the truth?  You need to look at it in a completely different way.  Let's start by gathering as much evidence as we can.  Not evidence in support of one hypothesis or another - just evidence, which consists of any and all facts that result from the true state of affairs.  In reality, any actual state of affairs results in a set of facts, or evidence, being left behind, and that evidence is just what we are able to observe as a result of that state of affairs.  Any complete collection of evidence is always consistent with the true state of affairs.  If we want to determine what that true state of affairs is, we need as many facts as possible, and we need to look at them all together so that we can postulate the one hypothesis from among all candidates that is most likely to produce that complete collection of evidence.  In this view, we consider the relationship between the full body of evidence and the likelihood of a hypothesis, not the relationship between the hypothesis and the likelihood of a single fact.  It is generally not reasonable to consider a single piece of evidence in isolation in support of some hypothesis, unless it happens that there is no more evidence available.

When we create a hypothesis, we must be cognizant of the total collection of evidence.  The hypothesis must be consistent with all the facts in evidence.  On the other hand, any potential hypothesis can be ruled out if there is one single piece of evidence that in inconsistent with it.  So to continue with our example, we start by gathering the evidence.
E1: Peanut shells found in the yard.
E2: Shells are in a single, neat pile, next to the bench.
E3: Peanuts are kept inside the house, and none were placed outside.
E4: There are no neighbors where animals could have obtained peanuts.
E5: No animals can get into the house.
E6: Kids live in the house.
E7: Your husband says he thinks squirrels did it.
Now, if we consider the hypothesis H1, we can rule it out, because birds would scatter the shells rather than leaving them in a pile.  H2 seems a bit more likely, but we know that squirrels can't get into the house, and there are no neighbors they could have taken peanuts from, so we rule out that hypothesis as well.  But we can come up with another hypotheses that is fully consistent with all the evidence:
H3: The kids took peanuts from the house and ate them in the yard.  
Is this hypothesis guaranteed to be correct?  Not necessarily.  It's still possible that
H4: Your husband did it, and lied about thinking it was the squirrels.  
All the evidence we have would also be consistent with H4, so we are unable to rule one or the other of those hypotheses.  Obviously, we need to consider additional evidence.  And in doing so, we need to remain open to the idea that a completely different hypothesis may be in order.

Again, we must gather facts without regard to their support for one hypothesis or another.  If we are leaning toward one hypothesis, we are likely to ignore some important evidence.  You may want to believe that your husband wouldn't lie, for example.  You consider another piece of evidence
E8: the peanuts were bought for the children to eat. 
And therefore, you may want to settle on H3 as your preferred hypothesis.  But objectivity is crucial when gathering evidence.  So you must take note of some additional facts.
E9: The peanuts were purchased yesterday.
E10: The kids weren't told about them yet.
E11: Your husband drank some beer on the bench outside last night.
E12: The shells were found first thing in the morning, before the kids went outside.
At this point, it's not looking good for your husband.  But it is worth nothing that both H3 and H4 are still consistent with all the facts in evidence.  And there is still one additional fact to come to light.
E13: When asked, the kids tell you they found the peanuts and ate them yesterday.
In the end, H3 appears to be the best hypothesis.  But that doesn't mean that H3 has been proven absolutely.  It could still be the case that the kids are covering for their dad, for example.

What can we make of all this?  There's nothing particularly wrong with using Bayesian analysis to evaluate evidence, but it is wrong to limit consideration to any single piece of evidence, or to anything less than all the available evidence.  A hypothesis should be formulated to take into account every available piece of evidence.  A single piece of evidence can be used to exclude a hypothesis from further consideration.  An isolated piece of evidence should not be seen as favoring or opposing a hypothesis.  Rather, the totality of evidence supports the best hypothesis.  The totality of evidence is always consistent with the true state of affairs.  If the true state of affairs includes some deception, then the evidence may be deceptive, but the evidence is always consistent with the truth.

To put this in perspective, Victor still insists that religious belief is based on evidence, not faith.
Oh please. So, the famous book in defense of Christianity was called "Faith that demands a verdict?" - Reppert
Faith is what leads one to ignore evidence - to fail to account for the full body of available evidence.  The book Evidence that Demands a Verdict does just that.  It has been extensively reviewed, and as the reviewers say, the jury is in and verdict has been handed down. has compiled a series of essays that examine this evidence much more objectively than Josh McDowell has done, and place it in context within the greater body of evidence available to anyone who isn't blinkered by religious faith.  In addition, they have made a list of other reviews of McDowell, found here.  The bottom line is that if Christians like Victor (and Josh McDowell) want to claim that their belief is based on evidence, then they need to look at all the evidence, not just the facts that support their favored hypothesis.  Otherwise, they're just letting faith govern their view of evidence.


  1. A thorough-going analysis of Dr Reppert's equivocal and tendentious stance. And this man is supposed to have been awarded a PhD? Reppert's lifetime work seems to have been nothing more than trawling for snippets of information in search of 'evidence' to prop up an already irrevocably credulous postulation.

    Now 2/3s through THIS BOOK, Faith vs Fact. It is perhaps a treatise that will come into its own over the next few years as a seminal work on the relationship between science and religion. A singularly good read through which many, if not most, of the ....i's... have been dotted and ....t's.... crossed that will render apologists' arguments little more than a collection of personal whinges.

  2. Here is one of the best articles I have ever read on this subject. Every last word is Pure Gold, and it would profit you immensely to read them all, thoughtfully and carefully.

    1. I read the whole thing. Lots of apologetic ranting and raving. It is remarkable how unskeptical you can be when you read something like that, and just take to to be "Pure Gold". I'll address the major arguments this guy makes.

      First, the "Argument from Intellectual Maturity": Objection 3: It seems that God does not exist, because children, fools, and other simpletons believe He does. Therefore, God is a delusion concocted by mental and emotional juveniles.

      I quote from Augustine:
      Even after the plain truth has been thoroughly demonstrated, so far as a person is capable of doing, the confirmed skeptic will insist on maintaining belief in his own irrational notions. This is due to either a great blindness, which renders him incapable of seeing what is plainly set before him, or on account of an opinionative obstinacy, which prevents him from acknowledging the truth of what he does see. Thence arises the woeful necessity of going to ridiculous lengths to expound yet more fully on what we have already made perfectly clear, in hopes that we might get through to those who close their minds to reason.

      And yet how shall we ever profit from our discussions, or what bounds can be set to our discourse, if we forever fall to the temptation of replying to those who reply to us? We must acknowledge that those who are so hardened by the habit of contradiction will never yield, but would rather reply out of stubbornness, even when they recognize their own error.

      The claim of being the adults in the room has been standard fare for Christians throughout the history of Christianity. Now some atheists are making a similar claim and the Christians are furious about it. i point this out not as a tu quoque, but simply to show the hypocrisy. The fact is that neither Augustine nor Hitchens has used this as an argument for or against the existence of God. What Shea has done here is to turn it into a straw man argument, so that he can then claim this argument is based on a fallacy. But the truth is that Shea has committed the fallacy.

      And you, planks length, as an unskeptical reader, don't recognize it as a fallacy. You simply call it "Pure Gold".

    2. Second, the "Argumentum Contra Suckers": Objection 4: It seems that God does not exist, for shepherd children, peasants, polyester-clad tourists from Jersey, and other people I regard as suckers say they see miracles. But any God worthy of the name would submit to my demand for experimental proof, not manifest Himself to such tacky people. God does not submit to my demands, therefore God does not exist.

      Once again, this is a straw man. It is not the argument that atheists make. This post was about evidence, and in particular, the need to look at all the evidence, not just the parts that you like. Yes, believers report seeing miracles, but skeptics don't. There's probably a good reason for that. Shea discusses thousands of witnesses at Fatima, "including atheists and skeptics". He neglects to mention that there is no agreement about what actually happened there, or the fact that those skeptics who were present didn't think that any miracle occurred.

      The believer only needs to hear someone say that they saw a miracle, and then he can claim there is "evidence" for his belief. He fails to dig deeper and obtain a more thorough understanding of the situation. He ignores all evidence to the contrary. The skeptic can't afford to do that. He's not looking for the right piece of evidence to make his case - he's more interested in getting the full story.

      Atheists don't argue that God does not exist due to the fact that he doesn't present the evidence they demand. Rather, they look at the accumulation of evidence, such as it is, and make a judgment based on what they know. They are aware that blinkered people report seeing miracles, and they are equally aware that objective observers don't. They are cognizant of the fact that there has never been one single case of a miracle being objectively and independently verified. That goes for the gospels, as well. If an unknown author writes of a miraculous event that was witnessed by many, it is still just a single report of the event. He could have written that the event was witnessed by every person on earth, but it's still just one report. If any of those alleged witnesses had gone and made their own independent reports of what they saw, then we'd have additional evidence to consider. But that's not the case. The Christian reads that single report and believes without question that there are many witnesses, so it must be true. The skeptic isn't so gullible.

    3. Third, the "Argument from Chronological Snobbery": Objection 5. It seems God does not exist, because if he did exist he would meet my demand for proof by giving a biblical author knowledge -- such as the soil composition of Mars or the design of a microchip -- impossibly ahead of the Bronze Age. He has not done this, therefore God does not exist.

      Yet another straw man. It's not simply the fact that the bible fails to reveal scientific truths, but more to the point, that the bible presents a variety of things as undisputed fact that are now known to be false. It really reveals a gross misunderstanding of scientific fact. Scientific theories change. But observed facts don't. The medieval notion of humors was never an observed fact. So the bible could have presented some information that would accurately predict what would eventually become an observed fact, and that would give us reason to believe that it's divinely revealed. Instead, what we see is evidence that that the bible was written without any special knowledge that wasn't common to people in that time and culture. And that's not proof that God doesn't exist, but it argues strongly that God had nothing to do with the authorship of the bible.

      Let me just take an example. In those days, the orbits of celestial bodies was thought to be circular. Observation has subsequently revealed that the orbits are elliptical. Well, not perfectly elliptical, because they are perturbed by other gravitational forces. But the observed fact is that orbits more closely approximate ellipses than circles, and that's not going to change. Now, it might be the case that some future discovery will reveal that space is curved slightly, to that the the planes of those ellipses is actually bent (meaning they're not real ellipses). None of that would change the basic observed fact. What we observe is still very nearly an ellipse. So if the bible told us that, it would reveal factual knowledge that would have been unknown to the authors.

      And there are also many other observed facts that are not even subject to modification by the advancement of science. For example, any existential fact like the existence of Uranus, or historical fact like the moon landing could have been reported in the bible. This would have been a great opportunity for God to provide objective evidence that he's more than just a fantasy. His failure to do so doesn't prove he doesn't exist, but it does give us reason to doubt.

      The bottom line is that Shea isn't honest enough to present an accurate picture of atheist's arguments. Instead, he presents straw men. And planks length isn't astute enough to recognize this for what it is. He merely sees words that agree with his beliefs, and that's good enough. No further investigation required.

  3. I am most happy that you read the article. Even though you failed to agree with it, I have faith (there's that nasty word!) that it has nevertheless planted a seed in your heart that may yet blossom into good fruit.

    We must never give up hope, even for those who seem most resistant to the Gospel, which has a way of working its way into the unlikeliest of places. Witness St. Paul, who for years actively persecuted the Church, yet ultimately became its greatest Apostle. So there's hope, even for im-skeptical.

    1. Reading the article only served to strengthen my conviction that Christian apologists don't have a leg to stand on. If they need to resort to misrepresenting the arguments of atheists, it only goes to show that they have no good answer for the actual arguments

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    3. I looked at that sec web link on McDowell. I think that a lot of that stuff has been answered by either Holding or Joe Hinman.

    4. They can answer these objections to McDowell, but the objections remain valid. He doesn't look at all the evidence. He only chooses to look at the evidence he needs to make his own story sound plausible. It' just like the way you only look at the creationists' literature about science.