From: jbrown@doc.bmd.trw.com
Newsgroups: alt.atheism
Subject: Re: Constructing a Logical Argument
Date: 22 Jan 93 08:45:01 MST

Newsgroups: alt.atheism
Subject: Re: Constructing a Logical Argument (long)
From: arromdee@jyusenkyou.cs.jhu.edu (Ken Arromdee)
Date: Fri, 22 Jan 1993 07:25:10 GMT

In article <1993Jan21.190024.591@doc.bmd.trw.com> jbrown@doc.bmd.trw.com writes:
>"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."
>    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.

If what you have pointed out is indeed a fallacy, consider that an argument
about the roundness of the earth contains the hidden assumption that light
doesn't bend in exactly the way to make the flat earth look round from space,
the hidden assumption that the people who claim to have circumnavigated it
are not lying, etc.

    I didn't say that hidden assumptions constitute lying.  Nor are the
    two cases strictly analogous.  When one says that "the earth is round",
    it means that the earth approximates a sphere in shape, although not
    exactly, the diameter through the equator being some miles longer than
    the diameter through the poles.  What you state as a "hidden assumption"
    concerning circumnavigation is not at all a hidden assumption in the
    logical sense as I used it above.  Of course, at the time that Magellan
    first circumnavigated the globe, one might have asserted that the report
    of the acting captain surviving Magellan was erroneous, and that any
    argument assuming the truth of the report included a hidden assumption.
    However, at the time, there was an independent body of evidence from
    other voyages which would generally corroborate the truth of Magellan's
    voyage even though it was the first true circumnavigation.

    This is not at all analogous to the situation I mention, since there is
    little evidence other than the various flood accounts as to the state of
    the earth at the time in question.	Certainly geologists have well
    thought-out theories as to what has happened to the earth in the past,
    but these are still essentially "educated guesses" and not factual
    observation.  Therefore to assume that the earth's topography was not
    different at the time of the Flood, however reasonable it may seem,
    constitutes a flaw in the argument.  Especially since the conclusion
    definitely states that there is no chance that the Flood could have
    occurred.  Not little chance, but *no* chance.  The strength of the
    argument is overstated as a result.

A hidden assumption that something did _not_ happen is not a hidden assumption
at all; the burden of proof is on you to prove that something happened.

--
Ken Arromdee (arromdee@jyusenkyou.cs.jhu.edu, arromdee@jhunix.hcf.jhu.edu)


    If there is outstanding evidence to support the hidden assumption such
    that it can be considered to be "generally accepted", then it can "go
    without saying", but one still runs the risk of forming an incomplete
    argument.  This may or may not be significant depending on the
    audience and their acceptance of what "goes without saying".  If the
    hidden assumption or unstated premise is only "generally accepted"
    among those of the same school of thought, then it is a logical flaw
    not to state and support the premise in an argument directed at those
    outside that school.

    And furthermore, the "burden of proof" is not on me at all.  In my
    discussion above I made no assertion that the Flood occurred or that
    the earth's topology actually changed.  I stated that it was a
    possibility, and thus the prior argument as stated was invalid.
    I do not have to assert, and thus substantiate, a possible event as
    having occurred, I only have to consider the possibility in order
    to *disbelieve* the argument as stated and to reject the strength
    of the argument as contained in the statement "...no such flood
    occurred."

    This is exactly analogous to the "I disbelieve in god(s)" vs. the
    "I believe there are no gods" distinction that you and others here
    in a.a. like to make.  The first statement makes no assertions about
    god(s), but simply does not accept the assertions of others.  There-
    fore there is no burden of proof.  The second statement makes an
    assertion in the negative, and therefore carries a burden of proof.

    Logic cuts both ways, it seems.

    Regards,

    Jim.

    Please send replies or comments to:  Jim_Brown@oz.bmd.trw.com
	
Xref: sparky alt.atheism:27117 sci.skeptic:22917