Burden of Proof Arguments                                                                 (Problems printing? Click here.)

At this point, you may find yourself wondering what happens if all the arguments on both sides succumb to counter arguments so that it turns out that there are no logically compelling arguments on either side of a question. (You don't find yourself wondering that? Well, pretend you do. Work with me here!) In order to fully answer that question, I have to make a distinction between personal opinion and knowledge. Here, I'm going to define "knowledge" as whatever beliefs we have that are appropriately backed up by evidence and logic. By "personal opinion," I mean whatever beliefs you happen to have. Since your own personal beliefs don't have to be backed up by evidence and logic, it follows that not all of your personal beliefs will count as knowledge. (And that's okay.) Now, if you're just worried about your own personal opinion, and it turns out that there are no logically compelling arguments on either side of a question, then you can just go on believing whatever it was you believed before. If you're worried about knowledge, the situation is a bit more complicated. If you find yourself asking, "given that there are no logically compelling arguments on either side of this question, what do we know?" The answer will depend on whether one side in the question happens to bear the burden of proof.

What To Do With Claims That Come Without Arguments

Because we stand on the shoulders of an multitude of giants, there are a great number of claims that that are already shown to be very, very, very, very likely to be true. I call this set of claims that are already proven "present knowledge," and the existence of present knowledge skews the proof process for new claims, depending on how congruent the new claim is with claims claims that are already proved. Here's how it works.

1. If a new claim turns out to be logically implied by our present knowledge, and has no argument for or against it, then the fact that it is implied by present knowledge implies that we should judge that this new claim is very likely to be true. If the implication from present knowledge is particularly strong, then we might even judge that this new claim is proven true merely by the fact that it is implied by things we already know.

2. If a new claim is merely consistent with present knowledge, and has no argument for or against it, then it's truth value is unknown. It is not known to be either true or false. Although the most rational course is to withhold judgement, rational people might chose to believe it true or believe it false, but no-one has the right to say that it is true or that it is false or that other people should or should not believe it.

3. If a claim is inconsistent with present knowledge, such that present knowledge tends to imply that it is false, and it has no argument for or against it, then we should conclude that it is probably false. Someone can can still believe such claims without being completely irrational, but such a believer would be dishonest if he went around telling people that the claim is true.

4. If a claim is clearly strongly contradicted by present knowledge, such that it can only be true if big chunks of our present knowledge are false, then, if it has no argument for or against it, we should conclude it is provably false. I suppose a person can believe a such a claim without being completely irrational, but such a person would be profoundly dishonest if he or she went around insisting that the claim was true and that others should believe it.

Present Knowledge

When I use the term "present knowledge," I definitely don't mean whatever it is that the majority of people happen to believe at any particular moment. Lots of things that lots of people believe have no basis whatsoever in any kind of evidence or logic. What I mean by present knowledge is the body of information that represents our best efforts so far at discovering the truth. These are the beliefs that, so far as we have been able to make out, are the most likely to be true of any beliefs that we might have. To say that we know something does not really mean that it is undoubtedly and unquestionably true. Rather it means that not only do we have good reason to believe it, we also have much better reason to believe it than we do for any competing belief. Thus for something to really count as part of present knowledge, it must already be backed up by evidence and logic. Beliefs that contradict present knowledge thus start out with at least one strike against them in that whatever argument established that present knowledge in the first place also tends to contradict whatever contradicts that present knowledge. To put it another way, if something contradicts established knowledge, then that by itself means that there is already an argument against it. If there is in fact no logically compelling argument for it, then we can and should conclude that it is false.

Contrascientific Claims

When a claim contradicts science it accrues a much higher burden of proof. This is because the present theories of science are supported by a huge accumulated weight of evidence, and all the evidence for any theory also counts against anything that contradicts that theory. For instance, Einstein's theory of Relativity says that faster than light ("FTL") travel is impossible, so any evidence for Relativity is also evidence against faster than light travel. This means that anyone who wants us to believe in FTL has an enormous burden of proof because all the evidence we've accumulated for Relativity is also logically evidence against his FTL claim.

Moral Claims

Morality is different. For one thing, there is much more expert disagreement about morality then there is about any other subject. For another, while it is perfectly fine for us to go through our lives ignoring the facts of physics and biology, it is deeply irresponsible for someone to go through life ignoring the facts of morality. People who violate morality are evil, and deserve to be shunned, yelled at, pelted with rotten fruit, or worse. But moral rules cannot exist without justification. If there is a rule that we all should follow, then that rule will come with a clear and explainable justification. If a purported moral rule fails to come with a clear justification, then it simply is not a moral rule. If someone tells you that something you want to do is morally wrong but cannot logically show that what you want to do will hurt anyone or anything, or that it will violate somebody's rights, or that there is some other logically sound justification, then you have no rational reason to believe that person.

Someone might argue that some moral rules are so well-established that they form part of present knowledge. The problem with that is that many things that have been believed to be moral rules for many generations have turned out to be either not moral rules to all or actually evil. As you review the struggle for human rights across the history of the world, there is one thing that is an absolute constant. Whatever the struggle, the people who were trying to maintain the old system of slavery, of racial segregation, of subjugation of women, of homophobia, of religious persecution or whatever were absolutely convinced that they, and only they, were fighting to preserve morality in the face of a rising tide of evil. The fact that a "moral" rule is well-established in the minds of the majority of people has nothing to do with whether or not it really is a moral rule. If it is a moral rule, then those supporting it will be able to cite good reasons in support of it. If it is not a moral rule, then those opposing it only have to show that it is not supported by evidence and logic.

For now, I'm going to give you a set of pairs of claims, some with answers, some without, for which you should determine which speaker bears the burden of proof at the start of the discussion. Remember that this class is about knowledge, rather than anybody's personal opinion. Therefore, you should not assign burden of proof based on whether or not you think a claim is true. You should assign it based on whether the speaker is making a positive moral claim, or a claim that is significantly inconsistent with our present knowledge.

1. Albert. The CIA killed John F. Kennedy.
Beth. No they didn't.

2. Charlie. The CIA overthrew the democratically elected government of Jacobo Arbenz of Guatemala in 1954.
Desmond. No they didn't.

3. Edgar. Ghosts exist.
Caitlyn. No they don't.

4. Gerald. Life exists on other planets.
Harold. No it doesn't.

5. Irene. It's morally wrong to kill innocent people for food when you have sufficient vegetables available.
Jessica. No it isn't.

6. Karen. It's morally wrong to kill innocent animals for food when you have sufficient vegetables available.
Linda. No it isn't.

7. Michelle. It's morally okay for two unattached consenting adults to have sex outside of marriage.
Nina. No it isn't.

8. Ophelia. It's morally okay to detonate nuclear devices in every city in the world.
Paula. No it isn't.

Burden of Proof Arguments

The idea behind burden of proof arguments is fairly simple. Some claims can be accepted without proof, so long as there is no logically compelling argument to the contrary. Other claims can not be rationally accepted without some logically compelling argument to back them up. Generally speaking, claims that we already have good reason to believe tend to fall into the first category, while new claims, that contradict our existing knowledge, fall into the second category. Thus burden of proof arguments are usually (but not always) used to reject new claims.

The way it usually works is that someone claims we should believe some new claim that contradicts our already established knowledge. He claims to have discovered a new form of radiation, or he knows who really killed Kennedy, or that George W. Bush is really Elvis, etc.. We ask him to give us a reason to believe him. He comes up with no real reasons, or maybe he just comes up with fallacious reasons. Nothing he says has persuasive force. We reject the claim. It's important to note that logically we're not just entitled to say "maybe, maybe not." We're logically entitled to say "not true." His failure to come up with reasons is itself a good reason to reject his claim. If we have to make up our minds, we should say no. If we don't absolutely have to make up our minds at that time, we can reasonably suspend judgement, but we still have a good reason to reject the claim.

The following are all good burden-of-proof arguments.

Nathan. So-called "cold-fusion" conflicts with well-established nuclear theory. People who claim cold-fusion exists have failed to produce any replicable results. Soooooooooo, cold-fusion does not exist.

Cindy. Believers in the 100-miles-per-gallon carburettor have failed to offer any credible evidence for it's existence. Therefore, no 100-miles-per-gallon carburettor exists.

Boyd. Astrologers have failed to offer any valid evidence that astrology has any special predictive power. Therefore, astrology has no special predictive power.

Steve. People who claim that cat-juggling is morally wrong have failed to offer any reasonable arguments against cat-juggling. Therefore, cat juggling is not morally wrong.

Giordanno. People who believe in Arkt-Rcckt-Siiv-Ek the Flaming Lizard Goddess have failed to offer any non-fallacious argument for her existence. Therefore, Arkt-Rcckt-Siiv-Ek does not exist.

It's important to remember that in evaluating these arguments we should take the position of a reasonable person who presently neither believes nor disbelieves in the conclusion, but who is willing to be persuaded by a reasonable argument. As in any argument, it's not necessarily irrational for someone to choose to disregard the argument and choose to disbelieve the conclusion. But such a person would not be deciding on rational grounds.

Nathan's argument is based on the fact that science at all times has an existing body of knowledge that it seeks to expand and refine. This body of knowledge of course grows and changes as science goes on. Sometimes it changes quite radically, with existing theories being thrown out entirely. But it doesn't change without a good reason, and when no good reasons are around, it actually has a good reason not to change. Why? Simply because science has again and again turned out to be right when the principle of not changing without good reason has been followed. People who have tried to change science without producing reliable evidence have invariably turned out to be wrong. Thus the fact that some claim conflicts with science is itself a good reason to reject that claim unless it is supported by evidence. If it isn't supported by evidence, then the mere fact it conflicts with established science gives us a rational reason to reject it. The burden of proof always lies on he who would change scientific knowledge.

Cindy's argument is based on the fact that society also has an existing body of knowledge that some people seek to expand and refine. This body of knowledge grows and changes roughly the same way as scientific knowledge. But it shouldn't change without a good reason, and when no good reasons are around, it shouldn't have to change at all. Thus the fact that some claim conflicts with society's established knowledge is itself a good reason to reject that claim unless it is supported by evidence. But notice that "established body of knowledge" is not the same as "common belief." Cindy's argument doesn't rely on the fact that no-one believes in 100-miles-per-gallon carburettors. It relies on the fact that such carburettors aren't part of the common experience of anyone she knows. No-one owns one, no-one she know knows anyone who owns one. Car dealers do not sell them, and so on. The established body of knowledge of society is the knowledge that society has built up through actual experience, not whatever the majority of people in society just happen to believe.

Boyd's argument is based on the same body of knowledge as Cindy's, only here, common belief tends to run the other way. Many or most people in our society believe that astrologers can predict events or divine personality features with an accuracy and scope that goes far beyond mere guesswork or cold reading. Boyd's argument relies on the fact that reliable information has only ever been produced by careful assessment of relevant data. Collecting data that has no connection with the subject has never worked in any other context, so it's unlikely that it would work for astrologers. This is enough to shift the burden of proof over to the astrologers. Since they bear the burden of proof, and have never met that burden, we have very good reasons not to believe in astrology.

Steve's argument relies on something completely different. Morality is something we never experience directly. We can experience things like pain and pleasure, constraint and freedom, feelings of shame and guilt, and know about other people experiencing those things, but no-one ever has a direct experience of something being moral or immoral. The morality of an action is something we have to figure out, and that can be difficult. It's especially difficult to come up with positive arguments in favor of things being morally allowable. (Can you come up with a positive argument that proves you have a right to go to college? Can you prove that anyone has a right to go to college? Or a right to not go to college?) So in moral reasoning (unlike logic) we have a general rule that any action is considered morally allowable unless someone can come up with a credible argument that it is morally wrong. Thus Steve doesn't have to offer any proof that cat-juggling is morally okay. The mere fact that his opponents haven't come up with any proof that it's not is enough to prove them wrong.

Giordanno's argument is logically similar to Steve's. Although people have feelings they attribute to the supernatural, no-one has actual experience of it. Since the number of possible supernatural entities is infinite, and most of them are such that if one of them exists, none of the others can, it makes sense to believe in none of them without incontrovertible evidence. Thus, even if everybody believes that they have experience of Arkt-Rcckt-Siiv-Ek the Flaming Lizard Goddess. Even if there are Flaming Lizard coloring books, folk stories, myths and unexplained scorch marks, as long as there's no evidence that can't be easily explained by ordinary means, (such as hallucinations, sleep paralysis, self-delusion, lying, and pious fraud) we have very good reason not to believe in Arkt-Rcckt-Siiv-Ek. (That's not to say we can't believe in the Flaming Lizard Goddess, just that we can't say we have a rational reason to do so.)

For some more practice, explain where the burden of proof lies for each of the following pairs of opposing statements.

9. Astrology can predict the future. Astrology cannot predict the future.
10. Chiropractic works. Chiropractic doesn't work.
11. Natural selection is true. Natural selection is not true.
12. Socialism is evil. Socialism is not evil.
13. We should ban affirmative-action. We should not ban affirmative-action.
14. Cigarette companies should be allowed to target black people. Cigarette companies should not be allowed to target black people.
15. Bill Clinton's Tomahawks hit a terrorist training camp. Bill Clinton's Tomahawks did not hit a terrorist training camp.
16. Elephants can wear people's pajamas. Elephants cannot wear people's pajamas.
17. Ray Charles is God. Ray Charles is not God.
18. We only use 10 percent of our brains. We don't only use 10 percent of our brains.
19. Deterrence will work on Saddam. Deterrence will not work on Saddam.
20. As originally written, the Constitution predominantly protected the interests of the ruling class. As originally written, the Constitution did not predominantly protect the interests of the ruling class.
21. It is wrong to alter one's state of consciousness. It is not wrong to alter one's state of consciousness.
22. Drug laws are justified by the prevalence of drug crime. Drug laws are not justified by the prevalence of drug crime.
23. A doctor's gut is more likely to be right than the appropriate tests. A doctor's gut is not more likely to be right than the appropriate tests.
24. Cat juggling is morally wrong. Cat juggling is not morally wrong.

Refuting Old Established Myths

So far, we've looked at burden of proof arguments aimed at rejecting some new claim. What about burden of proof arguments against old claims? Well, the logic is the same, except that the claim in question has had time to become an old claim. Consider the following conversation.

Raymond. You know that we only use ten percent of our brains, so if we could harness...
Reilly. Wait, wait, wait. Can you prove we only use ten percent of our brains?
Raymond. I don't have to. It's part of our established background knowledge. Burden of proof arguments only work on claims that conflict with our established background knowledge.
Reilly. But it does conflict with established knowledge. If it were true, neuroscience would only study ten percent of the brain, brain surgeons would only operate on ten percent, and so on. Nobody who actually studies the brain says we only use ten percent, and textbooks that show the brain describe a particular use for every part of it. I've never seen a picture of the brain that picks out ten percent and says, "this is the only part we use." Have you?
Raymond. Well, everyone I know says that we only use ten percent of our brains, so it is established background knowledge!
Reilly. No, that's just rumor. Knowledge is not the same as popular belief.

The trick to determining whether something is established background knowledge is to ask how a belief became common. If it became common because somebody studied the question and concluded that it was true, then it's established background knowledge. If it became common because it sounded good to some people, then it's not established background knowledge.

Thus there are three basic questions that should be asked about any burden of proof argument.

1. Does the conclusion of the argument fit with our established beliefs so firmly that we can't deny that conclusion without also implying that at least some of our background beliefs are false?

2. Are our background beliefs about this topic based on some kind of foundation?

3. Is it really true that the opposing side has no credible arguments against that conclusion?

If the answer to any of these questions is "no," then the burden of proof argument will not work. If the opposite conclusion turns out to fit our background beliefs, or if the beliefs the opposite conclusion doesn't fit aren't really well established, or the opposite conclusion's supporters can come up with a reasonable argument for their side, the burden of proof argument will fail.

Consider again Reilly's burden of proof argument against Raymond's claim that we only use ten percent of our brains.

Reilly. Raymond's claim that we only use ten percent of our brains conflicts with established background knowledge, so, since he has no credible argument, it is not true that we only use ten percent of our brains.

So long as Raymond's claim does conflict with our background knowledge, and the knowledge it conflicts with is genuinely established, the fact that he has no credible argument is itself enough to persuade us that his claim is not true. If his claim turns out not to conflict with genuinely established knowledge, then the burden of proof argument has no persuasive force.

Generally, anyone who makes a sweeping generalization or a moral claim bears the burden of proof, which means that if he fails to back up his claim with a compelling reason, we should conclude that his claim is false. Here are two examples of claims that bear the burden of proof.

Incomp says "If an organized basketball league exists then no-one can ever ride a spaceship over to the planet Mars."

Pseud says "It is immoral to wear grey socks with brown pants."

Now you might reply that these things don't seem connected to you, but Incomp and Pseud both reply that their claims are obviously true! That organized basketball just does preclude travel to Mars and grey socks with brown pants just is immoral. But no generalization is true without a reason. And if Incomp and Pseud can't back up either of their claims with reasons, then those claims are false, no matter how "obvious" they may seem. A feeling is not a reason.

Now, what if they both say "you can't prove us wrong, so we could be right!" Could it be true that organized basketball precludes travel to Mars? If it could, then you can't say it doesn't. Could it be true that it is immoral to wear grey socks with brown pants? If it could, then you can't say it isn't.

Well, I can. And I do. The point to remember is that we can prove Incomp and Pseud wrong because they bear the burden of proof here. If neither of them can come up with a reason to support his claim, then logically that claim is false. Not possibly false, just plain flat false.

If you don't think that failure to come up with a reason to support a generalization implies that that generalization is false, just remember that that also commits you to believing that the existence of organized basketball might mean we can't ever fly to Mars, and that it could be immoral to wear grey socks with brown pants, and a host of other equally ridiculous "possibilities."

Countering a Burden of Proof Argument

There are two basic ways that a burden of proof argument can be countered.  The first is to try to shift the burden by showing that present knowledge actually supports, or at least does not contradict the claim that is under attack, the second is to show that, contrary to the "no evidence" claim, there actually is an argument out there supporting the claim that is under attack

Matthew: The theory of Evolution Through Natural Selection must be wrong because it contradicts the Laws of Thermodynamics. 
Jadon:  Actually, the "laws" of thermodynamics aren't part of science any more. They've been reduced to Statistical Mechanics, which allows for occasional decreases in entropy, so it doesn't even appear to contradict Evolution Through Natural Selection.

Now, it's true that Matthew is not explicitly claiming that there's no evidence for natural selection, but the only way an argument like his can succeed is as a burden of proof argument, and so we should properly treat it as a burden of proof argument.

What would happen if Matthew was right? Well, that depends on whether there's an argument for Natural Selection.

If Matthew turns out to be right that science contradicts Natural Selection and no evidence supports Natural Selection, then Natural Selection will be proven false.

If Matthew turns out to be right that science contradicts Natural Selection but it also turns out that evidence does support Natural Selection, then Natural Selection will not be proven false, but Matthew will have succeeded in showing that it is not yet proven true either.

What would happen if Matthew was wrong? Well, that depends on whether there's an argument for Natural Selection.

If Matthew turns out to be wrong, but no evidence supports Natural Selection, then Natural Selection will be neither proven true nor proven false.

If Matthew turns out to be wrong, and it also turns out that evidence does support Natural Selection, then we will have good reason to believe Natural Selection and might even go so far as to think that it has been proven true.

Of course, if Jadon is right, Matthew's argument dies, and Natural Selection is not proven to be false by it. Notice that Jadon's is the standard type of counter argument, in which the the counter-arguer (Jadon) disputes a specific claim within the target argument without offering any direct argument in support of the claim he's defending. What happens in the other case is a bit more complicated.

Osvaldo: Evolution Through Natural Selection requires that the Earth be hundreds of millions of years old. But physics tells us that the Sun would have burned down to a dark cold cinder long ago if the solar system were that old. There isn't enough time for it to have happened, so Natural Selection didn't happen
Piper: The problem here is that there's tons of indisputable evidence for Natural Selection. There's the entire fossil record, the observed diversity of life on Earth and hundreds of confirming experiments. The mathematics is absolutely sound and there's absolutely no reasonable objection to the argument for Natural Selection. The argument for Natural Selection is just as strong, if not stronger than the argument for the Combustion theory of Solar Energy, so if one of these two theories is wrong, it's just as likely to be physics.

This is the only kind of case in which a direct argument can also function as a counter argument. This is because Osvaldo's argument can only work if it is the case that Natural Selection is not supported by any argument. If there's a reasonably credible argument for Natural Selection, Osvaldo's argument simply fails because the only way a "contradicts science" argument can possibly work is if there's no credible argument for the claim that is thought to contradict science. This means that Piper's argument is both a counter and a direct argument. Because it has this dual function, a lot depends on the strength of the argument cited by Piper here.

If the argument for Natural Selection is merely credible Osvaldo's argument collapses, but Natural Selection is not necessarily proven true.

However, if the argument for Natural Selection is more than merely credible, not only does Osvaldo's argument collapse, but Natural Selection might even be proven true.

In fact, if the argument for Natural Selection is compelling then not only does Osvaldo's argument collapse, but Natural Selection is proven true.

Fallacies

False Burden of Proof

The false burden of proof (or "appeal to ignorance") fallacy simply assumes that because some favored statement can't be proved false, it must be true. The difference between this and a genuine burden of proof argument is that, in the fallacy, there is no established body of knowledge and no justified logical principle that shifts the burden of proof over to the other side. The purported argument rests merely on the fact that the favored claim hasn't been absolutely disproved. Since almost no significant claim about the world can be absolutely disproved, this isn't an argument. Notice however that the person committing this fallacy doesn't merely say "you haven't proved me wrong, so I can still choose to stick to my previous belief" but goes further and asserts that "you haven't proved me wrong, so you should change your mind and agree with me." Let me demonstrate.

Colt. I understand that we have no solid evidence that ancient intelligent fungi from Yoggoth are not the secret masterminds behind the explosion of New Age bookstores in this country, but you haven't proved that the Fungi from Yoggoth aren't behind the new age craze, so I'll go on believing it and you and I will have to agree to disagree on this.
Fabre. Darn right! And you have to agree that since you can't prove that crystals don't have mystical healing powers, everyone should agree that they do!

Notice that Colt doesn't claim to have proved anything. All she does is point out that the fungal mastermind theory hasn't been disproved, and so she is going to go on believing it. That's her choice to make. She doesn't expect anyone to agree with her, and doesn't claim to have offered an argument. Not so Fabre. He claims that because the healing crystal theory hasn't been disproved, we should all regard it as proved! That's pretending to have an argument, and so it's a fallacy. Here's another example.

Paulette. Christianity and Islam have about the same amount of evidence in their favor. However, people believed in Christianity before anyone believed in Islam, so Islam bears the burden of proof here.

There are two things wrong with this argument. First, the mere fact that people believe something is not enough to shift the burden of proof for an undecided observer. It's true that someone who's already a Christian is entitled to demand a high standard of proof from a Muslim who's trying to convert him, but someone who's already a Muslim is equally entitled to demand an equally high standard of proof from a proselytizing Christian. The other problem here is that, if this was a genuine argument, it wouldn't support Christianity at all. The only religions it would support would be Pagan religions like Druidism or Odinism, or, let's face it, Neanderthal shamanism!

Irrational Proof Standard

The fallacy of irrational proof standard is basically the same thing in the other direction. Observe.

Gunther. The theory of natural selection has passed every scientific test for a theory. It has resisted all kinds of attempts at disconfirmation, and has proven to be right in a major conflict with physics. It makes correct predictions in every situation we can observe, and adequately explains every aspect of biological evolution as represented by the fossil record. Finally, it has proved to have applications outside of biology, leading to very fruitful insights, and even new sciences, in neuroscience, psychology, sociology and even computer science.
Creighton. But you still can't prove it true beyond a shadow of a doubt! In fact you can never prove absolutely that evolution happened. So obviously natural selection has not been scientifically proved!

The problem with Creighton's argument is that nothing we know about our universe is proved beyond a shadow of a doubt. The facts mentioned by Gunther actually make natural selection one of our stronger scientific theories. In some ways, Relativity and Quantum Mechanics are shakier than Natural Selection. People like Creighton usually believe many, many things on evidence far weaker than that supporting natural selection. Notice that it's not irrational for Creighton to say. "There's still some room for doubt, so I personally can choose not to believe the theory of Natural Selection." That would be his free choice. What's irrational is pretending that that extremely small room for doubt should convince other people to think that Natural Selection has not been proved to the same standard as other scientific theories.

Logic vs. Personal Belief

Finally, I want to remind you that while no-one is entitled to claim that anyone should believe something that is not supported by logic, everyone is entitled to her own opinion, whether it's logically supported or not.

Colt. I understand that we have no solid evidence that ancient intelligent Fungi from Yoggoth are not the secret masterminds behind the explosion of New Age bookstores in this country, but you haven't proved that the Fungi from Yoggoth aren't behind the new age craze, so I'll go on believing it and you and I will have to agree to disagree on this.
Fabre. Darn right! And you have to agree that since you can't prove that crystals don't have mystical healing powers, everyone should agree that they do!

This class is only about what we know, not about what we only believe. Colt can't say that she's proved that that the Fungi from Yoggoth are to blame for those new-age bookstores, but there's nothing wrong with her choosing to believe it.

Exercises

Here are some exercises. As usual, the exercises denoted by letters come with answers. The ones denoted by numbers don't. Your mission is to scaefod each pair. Look for good burden of proof arguments as well as instances of false burden, irrational standard, Self Contradiction and people getting confused between knowledge and opinion.

25. Toker. I've been smoking marijuana regularly for thirty years. I've been a stable and productive member of society all that time. I've never been in trouble, missed work, or hurt anyone. I've never driven while stoned. You haven't given me any reasons why marijuana smoking is morally wrong. In fact, all the arguments for the immorality of marijuana fail for one reason or another. So it's clearly not morally wrong to smoke marijuana.
Citlalli. Can you prove that some time in the future, maybe tomorrow, someone won't come up with a logically compelling argument? Can you prove that there's no argument out there waiting to be discovered? You can't, so it is morally wrong to smoke marijuana.

26. Geovanni. Right now, the evidence says that there is no intelligent life in outer space. We have received no radio signals that cannot be accounted for by natural phenomena, and there is no physical evidence of any kind supporting the idea that intelligent life exists elsewhere in the universe. So the probability is that there is no intelligent life in outer space.
Katie. The trouble with that argument is that no one has ever been into outer space to look. We haven't even visited the nearest star, so you can't even prove that there's no intelligent life there. Since no one has proved that there is no intelligent life in other solar systems, it follows that there is intelligent life in some other solar system.

27. Helen. Every argument ever offered for the existence of Vuntag has been deeply logically flawed. None of them have been the kind of argument that anyone would accept if it didn't have "Vuntag exists" as its conclusion. Since there is no remotely logically compelling argument for the existence of Vuntag, it follows logically that Vuntag doesn't exist.
Drake. Apart from the fact that none of the arguments for the existence of Vuntag are any good, you don't have any reason to think that Vuntag doesn't exist. In fact, there is no positive argument for the nonexistence of Vuntag, so it follows logically that Vuntag does exist.
 
28. Dim Sum. We've gone over the rubble with searchers, ground penetrating radar, and search dogs. We haven't detected any movement or sound for the past three hours, so we are forced to conclude that no one is left alive in there, and we therefore should not mount a massive effort to uncover more survivors.
Satay. But you cannot prove that there is not some survivor trapped in some pocket of air somewhere in there, so we should immediately mount a massive effort and go on until we have found every survivor. (Answer)

30. Marcelo. We've done dozens of properly controlled scientific studies, and they all show that acupuncture works at relieving pain. We've also found theoretical reasons, and independent evidence that strongly suggests that acupuncture works by stimulating the release of endorphins. No one who has applied the techniques correctly has failed to produce a relief of pain that is far superior to placebo. So now we have scientific proof that acupuncture works.
Stanley. But can you prove that acupuncture really was the mechanism that relieved the pain in every one of your studies, and in every time that acupuncture was ever applied? You can't, can you? So we don't have scientific proof that acupuncture works!

31. Nigel. Well, I admit that no one has ever been able to get the same results that I do with the same experiment, but if we all accept my new theory, we can see that my results make sense.
Millicent. But your new theory flatly contradicts the best established theory in biological science!
Nigel. Yes, so my results justify overturning that theory.
Millicent. Not until other scientists start getting the same results you do!

32. Marsala. I've seen a summary of the results of all the studies that have ever been done comparing the murder rates in states with and without the death penalty. After all the corrections have been made to account for all the variables and other demographic factors, it turns out that there's no evidence that the death penalty has any deterrent effect whatsoever. Since the effect would show up in a difference in murder rates if it existed, we should conclude that there is no deterrent effect.
Naan. You're misunderstanding the nature of statistics. Actually, the evidence for the deterrent effect of the death penalty holds up pretty well. You have to understand that there are all kinds of things that can go wrong with a study. There may be bias, for instance. Or the data may be incomplete. Or the researchers might have compared demographically dissimilar groups. So it should be clear to you now that we can discount these studies, and should affirm that the death penalty does have a deterrent effect.

Thinky Questions (The answers to these questions are given in the chapter above, so I don't answer them below.)
a. What does "burden of proof" mean?
b. What's the difference between "knowledge" and "opinion?"
c. Who bears the burden of proof in any moral question?
d. How do burden of proof arguments work?
e. How can burden of proof arguments go wrong?
f. Explain false burden of proof.
g. Explain irrational proof standard.
h.
i. If something was believed by our ancestors, is that enough to make it knowledge?
j. Are we morally obligated to believe what our parents and grandparents believed?
k. Are we ever morally obligated to avoid evidence and logic?
l. Can a belief be "knowledge" if it is not backed up by evidence?
m. If you disagree with a person in power, do you logically bear the burden of proof?
n. If you disagree with a religious leader, do you logically bear the burden of proof?
o. If you disagree with the product of our best thinking so far, do you logically bear the burden of proof?
p. If you are claiming something is morally wrong, do you automatically bear the burden of proof?
q. If you are making a definite claim, do you automatically bear the burden of proof?
r. If something hasn't been proved absolutely, does that mean it isn't proved at all?

Answers to Exercises That Have Answers

Remember that the answers I give here all depend on the background knowledge that is generally available. This background knowledge may be different from your personal opinion, so from your personal point of view, the burden of proof will always lie on the person who disagrees with you. From the point of view of logic, however, the burden of proof lies on he who makes a moral claim, and on he who makes a claim that is inconsistent with the best supported information currently available.

I will warn you, however, that there's sort of a trick question to all this. You can think about things that makes this all more complicated as you're reading the answers, and especially think about the cases where you disagree with me about who bears the burden of proof, and I'll explain the trick at the end.

1. Here, the burden of proof lies on Albert. Many people have made many claims about the Kennedy assassination, but none of these claims is generally accepted by historians. And although the CIA and its agents have assassinated foreign leaders, and have done many nasty things to American citizens, it has never killed any American government officials, so assassinating an American president would be inconsistent with its established pattern of behavior.

2. Here, Desmond bears the burden of proof. Not only is the CIA overthrow of the Arbenz government extremely well documented by a variety of sources, the CIA is well-known to indulge in such actions on a regular basis. (However, if the CIA's actions in Guatemala weren't already documented, then it would be Charlie who bore the burden of proof. And on a personal basis, if you're not already aware of this documentation, then Charlie could bear the burden of proof as far as you're concerned.)

3. Edgar bears the burden of proof here. No ghost story has ever been reliably verified. Everything science has ever established in physics and biology implies that ghosts are absolutely impossible. Belief in ghosts thus absolutely contradicts all relevant established knowledge. If Edgar wants any rational person to even think that ghosts might exist, then he has to come up with some logically compelling argument to that effect.

4. Believe it or not, Harold bears the burden of proof here. While the probability of life appearing on any given planet out there is extremely small, the number of planets in the universe is so unimaginably vast that the probability that life will appear on some other planet is actually extremely high. Since the probabilities are in favor of Gerald, it follows that Harold bears the burden of proof.

5. Irene is making a moral claim, so she bears the burden of proof. It may be an easy burden to meet, but she bears it.

6. Again, the person making the moral claim bears the burden of proof.

7. Here, Nina bears the burden of proof. Notice that although Michelle raises the issue of morality, she is actually stating that there is no moral rule here. Nina is the one claiming that there is a moral rule, so she bears the burden of proof.

8. Paula. Even though Paula's burden of proof is amazingly easy to meet, she is still the one that bears the burden here.

Did you notice the complication? Did it ever happen that you didn't know where the burden of proof lay until I explained it? Did it ever happen that you disagreed with me about where the burden lay? Sometimes the location of the burden of proof is unclear, and it may take careful argumentation to establish just where the burden really lies. Thus burden of proof is more complicated than I have made it seem so far. In fact, important questions sometimes turn out to depend critically on the issue of burden of proof, and so later in the course we will spend time on burden of proof arguments.

9. Astrology can predict the future bears the burden here. No-one has every supported astrology with evidence, and everything we know says it can't work
10. Chiropractic works bears the burden here. No-one has every supported chiropractic with evidence, and everything we know says it can't work
11. Natural selection is not true bears the burden here. All the evidence supports it, no evidence contradicts it.
12. Socialism is evil bears the burden. You say something is evil, you have to support it.
13. We should ban affirmative-action bears the burden. You say we should do something, you have to support it.
14. Cigarette companies should not be allowed to target black people bears the burden. You want to ban something, you bear the burden.
15. Bill Clinton's Tomahawks hit a terrorist training camp bears the burden as a definite claim that needs support.
16. Elephants can wear people's pajamas bears the burden. Duh.
17. Ray Charles is God beard the burden.
18. We only use 10 percent of our brains bears an enormous burden. Every part of the brain has been shown to be used.
19. Deterrence will not work on Saddam bears the burden. Why would Saddam be different from everybody else?
20. As originally written, the Constitution predominantly protected the interests of the ruling class bears the burden. It's a very controversial claim among historians.
21. It is wrong to alter one's state of consciousness bears a huge burden of proof.
22. Drug laws are justified by the prevalence of drug crime bears the burden of proof.
23. A doctor's gut is more likely to be right than the appropriate tests bears an enormous burden of proof. Guts have never been shown to work as diagnostic tools.
24. Cat juggling is morally wrong bears the burden.

25. Toker gives a good burden of proof argument. Citalli commits the irrational standard fallacy.

26. Giovanni's argument sets an irrational standard for the possibility of extra-solar life. The universe is so big that billions of years could pass before radio signals from another civilization could reach us, and when they did, they would be so faint as to be undetectable.
Katie's argument sets a false burden of proof on the negative side. Just because no one has proved that each individual other solar system is bereft of intelligent life doesn't mean that any of those solar systems actually contain intelligent life.
Independently of these arguments, I think a logically compelling argument could be made for the existence of extra-solar intelligent life based on the size and general properties of the universe, but Katie does not make this argument. She makes a false burden of proof argument, and so the argument she actually gives is a bad one.

27. Drake is giving an opposing argument. (In order for him to counter Helen's argument he would have to come up with some reason why non-believers in some specific god would bear the burden of proof.) Helen's argument has the logical structure of a good burden of proof argument. If it is true that none of the arguments offered for the existence of God are logically good, then it follows that the most rational conclusion that can be drawn about God is that she does not exist. This is because believers in any supernatural entity, like Vishnu or Casper the friendly ghost, always bear the burden of proof. Drake's argument is a classic example of a false burden of proof. While he is of course entitled to believe whatever he chooses to believe, he is not entitled to assert that the lack of any argument apart from the burden of proof argument proves that God exists. At the most, he can reasonably claim that he does not accept burden of proof arguments as compelling, and thus does not accept that the nonexistence of God has been proved. (Of course, such considerations also apply to the nonexistence of Vishnu and the nonexistence of Casper the friendly ghost.)

28. Satay gives no reason why Dim Sum should bear the burden of proof, she doesn't directly address any of Dim Sum's premises, so hers is an opposing argument. Satay's argument imposes an irrational proof standard on Dim Sum by implying that an exhaustive search of the rubble is not enough to eliminate any realistic hope of finding survivors. While it is true that most search teams are willing to keep working as long as there is a real possibility of finding any survivors, they are not obligated to do so when the real possibility of finding survivors has been eliminated

29. On the logic given above, the testimony of believers cannot be taken as proof that Vuntag exists. Jasmyn is basically attacking an earlier, unstated argument that testimony can prove the existence of Vuntag by showing that it's basic principle (testimony proves existence) would also prove the existence of another god whose existence is incompatible with that of Vuntag. Efren attempts to rebut Joan's argument by claiming there's a difference between the two cases. However, this "difference" is just his presumption that Vuntag exists to provide divine revelation, a presumption that could equally well be made for Phobodisda. Since Efren wants to allow this presumption for his side but deny it for the other side, his argument contradicts itself and thereby fails.

30. Stanley does not contradict any of Alan's premises, and his conclusion does not imply any specific comments on Alan's reasoning, so again it's an opposing argument. Stanley commits the fallacy of irrational proof standard. There is no scientific experiment that can meet the kind of standard he is trying to impose.

31. Nigel commits the fallacy of self contradiction. He wants his theory to be accepted on the extremely flimsy grounds that he, and only he, gets results that are consistent with it, and yet he wants the other theory to be rejected even though it is the best established theory in biological science.

32. Has Naan given any evidence for the deterrent effect of the death penalty? Has Naan given any evidence that any of the studies were biased? Has Naan given any evidence that any of the data was incomplete? Has Naan given any evidence that the researchers compared demographically dissimilar groups?
It is a fact that science and public policy depend heavily on studies. Both science and public policy would be impossible if there were no good studies. Therefore, there must be studies out there that everyone agrees are good studies. Has Naan given any evidence that any of the studies were conducted differently from all these studies that everyone agrees are good studies?  He hasn't, so his argument is a red herring.

Copyright © 2013 by Martin C. Young

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