Burden of Proof Arguments
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More BOP fallacies:
Counter arguments:
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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