From: jbrown@doc.bmd.trw.com
Newsgroups: alt.atheism
Subject: Re: Constructing a Logical Argument (long)
Date: 21 Jan 93 19:00:24 MST

Subject: Alt.Atheism FAQ: Constructing a Logical Argument
From: mathew@mantis.co.uk (mathew)
Date: 18 Jan 93 12:08:16 GMT

                       Constructing a Logical Argument

[...]


ARGUMENTUM AD IGNORANTIUM

Argumentum ad ignorantium means "argument from ignorance".  This fallacy occrs
whenever it is argued that something must be true simply because it has not
been proved false.  Or, equivalently, when it is argued that something must
be false because it has not been proved true.  (Note that this is not the
same as assuming that something is false until it has been proved true, a
basic scientific principle.)

    Mathew, I would differ with you here.  Science does not assume that
    an assertion is false until it is proven true.  I would say that
    the scientific principle is that an assertion is undecidable until
    proven either true or false.

    If it were the case as you stated above, then science would not follow
    the laws of logic and science would not be logical; a concept which I
    reject as fundamentally flawed.  A science must be logical in order to
    properly be called a science.

    An example:

    A physicist asserts that quarks exist.  He may have reasons to make
    such an assertion based on the behavior of larger particles.  The
    associated theory of quark interaction may even be useful in
    understanding the behavior of larger particles and explaining why
    they behave as they do.  But until an experiment can be devised
    that can measure a phenomenon that would directly indicate the
    existence or non-existence of quarks, the truth of the assertion
    is undecidable.  Nevertheless, the theory may in fact be useful
    even if the existence of quarks cannot be directly demonstrated.

    (Note:  It's been awhile since I directly followed this aspect of
    physics.  I am not aware if such an experiment has been designed
    or not.)

    Another example, (close to the heart of some atheists here):

    Someone asserts that pink unicorns exist.  He may have his own
    reasons to make such an assertion.	We can evaluate his reasons
    and decide from our point of view how valid they are, and based
    on this evaluation we can assign a likelihood to the truth or
    falsity of the assertion.  We can also determine if the assertion
    is useful in explaining or predicting other phenominae, and if
    such usefulness is lacking, we can use the Occam's Razor principle
    (being itself an undecidable assertion or premise) to dismiss
    the assertion in our own minds.  But from a scientific standpoint,
    the assertion is undecidable.

    This is where human judgment and reasoning come into play.	Due to
    our experiences and general understanding of the universe we can
    get a "gut feel" (intuition) as to what makes sense and what doesn't.
    We assess that quarks are far more likely to exist than pink unicorns
    simply because we have no parallel for unicorns, pink or otherwise,
    in the animal kingdom.  There are no "horned horse" fossils, for
    example.  However, one might reasonably accept the existence of
    quarks due to the usefulness of quark theory to predict particle
    interactions.  One might say that particles behave as if quarks
    existed, even if they don't.  On the other hand, a theory of pink
    unicorns doesn't give rise to any sort of useful predictions for
    any observable phenomenae, so its value as a theory is nil.

    So in the final analysis, science itself can make no final determination
    as to whether quarks or pink unicorns exist or not.  Not until a proper
    experiment is devised which would produce an observation that supports
    or denies the assertion in question.  Thus, such an assertion is
    undecidable on the basis of the scientific method, not false until
    proven true.

[....]

Note that this fallacy does not apply in a court of law, where one is
generally assumed innocent until proven guilty.

Also, in scientific investigation if it is known that an event would produce
certain evidence of its having occurred, the absence of such evidence can 
validly be used to infer that the event did not occur.  For example:

"A flood as described in the Bible would require an enormous volume of water
to be present on the earth.  The earth does not have a tenth as much water,
even if we count that which is frozen into ice at the poles.  Therefore no
such flood occurred."


    Here we might mention another logical fallacy.  I don't know the Latin
    expression, but I'd describe it as the Fallacy of Hidden or Unstated
    Premises/Assumptions.

    Your statement above, intended to illustrate Denial of the Consequent
    (if I have my terms correct), actually includes the fallacy of hidden
    assumptions.  The hidden assumption is that the topography of the earth
    has not significantly altered since just before the time of the Flood.
    Actually, we do not know if such a change occurred or not.	There is,
    in fact, plenty of water on the earth to cover essentially the entire
    land surface now in existence if seas at the time just prior to the Flood
    were shallower and the atmosphere and the ice caps contained more water
    than they do now.  The Bible describes a period of severe geological
    upheaval during the Flood which count account for the deepness of the
    seas since.

    It is, of course, up to each individual to assess for him or herself
    the probability of such a change in the earth's topography to occur.
    But the possibility that such an event could have occurred is enough
    to falsify the second sentence stating that the earth does not have
    even a tenth of the water required.  The earth may not have a tenth
    of the amount needed today with our deep oceans and high plateaus,
    but who can say what the exact topography was at any particular
    moment in the remote past?	This possibility negates the "therefore"
    and the "no such ... occurred" in the conclusion.  One might reason-
    ably argue that the probability of the Flood occurring is small, but
    to say "no such flood occurred" has not been conclusively demonstrated
    since statement two has inherent hidden premises that have not
    themselves been demonstrated to be true.  Therefore, the arguement
    is "invalid" by the definition previously given in your post.

[....]

ARGUMENTUM AD POPULUM

This is known as Appealing to the Gallery, or Appealing to the People.  To
commit this fallacy is to attempt to win acceptance of an assertion by
appealing to a large group of people.  This form of fallacy is often
characterized by emotive language.  For example:

"Pornography must be banned.  It is violence against women."

    This argument is not necessarily flawed if, in fact, one demonstrates
    that pornography IS violence against women and that violence against
    women is bad and should be banned.	The argument only suffers from
    missing intermediate propositions and not from Argumentum ad Populum.

"The Bible must be true.  Millions of people know that it is.  Are you trying
to tell them that they are all mistaken fools?"

    Now this is actually Argumentum ad Populum.

[....]

ARGUMENTUM AD VERECUNDIAM

The Appeal to Authority uses the admiration of the famous to try and win
support for an assertion.  For example:

"Isaac Newton was a genius and he believed in God."

This line of argument is not always completely bogus; for example, reference
to an admitted authority in a particular field may be relevant to a
discussion of that subject.  For example, we can distinguish quite clearly
between:

"Stephen Hawking has concluded that black holes give off radiation"
and
"John Searle has concluded that it is impossible to build an intelligent
 computer"

Hawking is a physicist, and so we can reasonably expect his opinions on black
hole radiation to be informed.  Searle is a linguist, so it is questionable 
whether he is well-qualified to speak on the subject of machine intelligence.

    Good point, Mathew.  Many people I've had discussions with reject ALL
    appeals to authority.  Actually, as you say, an appeal to authority is
    not fallacious where it can be demonstrated that the authority is an
    expert on the subject and can be reasonably accepted as knowing what
    he or she is talking about.

    By the way, based on this line of thinking, Jesus can be considered as
    a reliable authority on spiritual, moral, and theological issues if it
    can be demonstrated to a person's satisfaction that He is, in fact, God
    in the flesh as He claimed.  Likewise, the apostles, including Paul,
    derive their authority on these same issues through Jesus.

[....]

CONVERSE ACCIDENT / HASTY GENERALIZATION

This fallacy is the reverse of the fallacy of accident.  It occurs when one
forms a general rule by examining only a few specific cases which are not
representative of all possible cases.

For example:
"Jim Bakker was an insincere Christian.  Therefore all Christians are
insincere."


SWEEPING GENERALIZATION / DICTO SIMPLICITER

A sweeping generalization occurs when a general rule is applied to a
particular situation in which the features of that particular situation
render the rule inapplicable.  A sweeping generalization is the opposite of a
hasty generalization.

    Please provide an example.	I'm not sure what form it would take compared
    to that given above.


PRINCIPIO PRINCIPII

This is known as Begging the Question.  The fallacy occurs when one assumes
as a premise the conclusion which one wishes to reach.  Often, the 
proposition will be rephrased so that the fallacy appears to be a valid
argument.  For example:

"Homosexuals must not be allowed to hold government office.  Hence any
government official who is revealed to be a homosexual will lose his job. 
Therefore homosexuals will do anything to hide their secret, and will be open
to blackmail.  Therefore homosexuals cannot be allowed to hold government
office."

Note that the argument is entirely circular; the premise is the same as the 
conclusion.  An argument like the above has actually been cited as the reason
for the British Secret Services' official ban on homosexual employees. 
Another example is the classic:

"We know that God exists because the Bible tells us so.  And we know that the
Bible is true because it is the word of God."

    Consider the following.

    Joe says that he owns a red car.  And we know that Joe is telling the
    truth because his car is red.

    This is a argument of the same form as the "God exists" argument above.
    But the argument is not actually circular.	The conclusion affirms
    the antecedent with the words "...BECAUSE his car is red".  If "...his
    car is red" is merely an assumption, then the argument becomes circular.
    But all we need do to avoid circularity is to show that the car is
    indeed red.  If the statement "...because his car is red" is a statement
    of factual observation, then circularity is avoided.

    To show that the Bible is the Word of God, all we have to do is
    demonstrate that the Bible does what no human could do, precisely
    fortell future events.  Or that the Bible tells its story from a
    perspective that would not occur to a human writer without inspiration
    from God.  Such has been demonstrated to the satisfaction of some.
    So if the statement "...because it is the Word of God" can be
    demonstrated to be true, then the argument is not circular.

    Back to the example.

    In addition, let's consider that Tana also says that Joe's car is red.
    And Brian says so.	And Ted.  And 36 others also.  Even without seeing
    the car, we might reasonably conclude that Joe's car is most likely
    to be red as asserted.  We would not consider such an argument as
    circular due to the weight of corroborative testimony.  We might
    decide to call into doubt the testimony if no other evidence was
    forthcoming, but the argument would not be circular.

    The fact is that the Bible is not a single book but an anthology
    of writings by 40 or so authors testifying to the existence of God.
    You might decide that the testimony of these various 40-odd writers
    is false, but the Bible is not circular in stating that God exists
    and simultaneously claiming to be the Word of God written by men
    inspired by God.



COMPLEX QUESTION / FALLACY OF INTERROGATION

This is the Fallacy of Presupposition.  One example is the classic loaded 
question:

"Have you stopped beating your wife?"

    I've always wondered what this one was called.  Thanks.

[....]



ARGUMENTUM AD NAUSEUM

This is the incorrect belief that an assertion is more likely to be true the
more often it is heard.  An "argumentum ad nauseum" is one that employs
constant repetition in asserting something.

    This is one I see quite often; especially here in a.a.



SHIFTING THE BURDEN OF PROOF

The burden of proof is always on the person making an assertion or
proposition.  Shifting the burden of proof, a special case of argumentum ad
ignorantium, is the fallacy of putting the burden of proof on the person who
denies or questions the assertion being made.  The source of the fallacy is
the assumption that something is true unless proven otherwise.

    True, except that when one denies an assertion or propostion, the
    denial itself is an assertion in its own right and therefore
    carries a burden of proof for the truth/falsity of the denial.  If one
    merely questions an assertion, or refuses to accept its validity
    rather than outright denying it, then there is no burden of proof.

    This is the old "I disbelieve in god(s)" versus the "I believe
    that there are no gods" distinction which is so oft quoted in
    this group.


    Mathew,

    Congratulations on a well written article overall.	I enjoyed it and
    found it quite informative.

    Regards,

    Jim B.
    Email comments/responses to:  Jim_Brown@oz.bmd.trw.com