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Dear Will:
I received from you the following post. Although I do not take
issue with the substance of your argument, I do take issue with its form and
the ultimate conclusion. Here's why:
On Thu, 9 Apr 1998, Tom Mount wrote:
> The statement was about a bulhman model I happened to agree with the answer
> Trout gave and showed the list why, by running bulhman model tables.
> Tom
Tom, let's go back and parse the question, since it's clear
the question was lost among all the posturing in this thread:
7. Oxygen can be employed to increase safety regarding DCS or it
can be used to shorten decompression time by permitting the diver to
conduct the 10fsw stop at 20fsw.
True/False.
OK first, "or" makes this two statements, making the entire question
false if either individual statement is false. What we
get is:
[1] "Oxygen can be employed to increase safety regarding DCS"
Clearly, this is true.
[2] "it can be used to shorten decompression time by permitting the diver to
conduct the 10fsw stop at 20fsw."
The statement "it can be used to shorten decompression time"
is also obviously true, which is what I think you were
getting at with your deco examples. Again, nobody is
going to argue with that part - obviously O2 can be
used for accellerated decompression.
The problem comes with the next part; "by permitting the diver to
conduct the 10fsw stop at 20fsw" which describes HOW it is
that it can be used to shorten deco.
IANTD uses Bulhmann tables in the manuals, and promotes
Buhlmann-based deco software packages.
I assume TDI does as well.
The simple fact is that if you are using Buhlmann,
and you are breathing pure O2, conducting the 10fsw stop
at 20fsw will not make one second of difference in
your hang time.
And that makes the second part false, which makes
the entire statement false - which makes the answer "FALSE".
[Cory resumes here.] Question no. 7 is a disjunct, to use the logician's
term. As such, it is true if EITHER of the statements contained therein is
true. For instance, "either Madonna is a female or else she holds the
record for the deepest scuba dive" is true, because the first part of the
disjunct--that is, "Madonna is a female"--is true.
Will, in your analysis of Question no. 7, the answer is TRUE because, as you
yourself point out, the first statement regarding the use of oxygen to
increase safety against DCS is true. It matters not that the second
statement is false, in purely logical terms, because this is a disjunctive
question. Had it been a conjunct--i.e., "and"--you certainly would be correct.
Again, I must reiterate that I do not take issue with your
substantive analysis. I am only pointing out one of the formal errors in
your analysis.
Respectfully submitted,
Cory J. Briggs, NAUI no. 14693L
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