NetNews Usenet Archive 1992 #23/NN_1992_23.iso/spool/sci/logic/1713

Text File | 1992-10-14 | 1.9 KB | 45 lines

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From: [e-mail] (Gary Merrill)
Subject: Re: A only if B
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Date: Wed, 14 Oct 1992 18:57:37 GMT
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In article <[e-mail]>, [e-mail] (Frank Teusink) writes:
|> I agree totaly in the mathemathical sense. But I think that when
|> we use the phrase "only if" in language, the "if" part is often
|> implicite. I would not say "Tom will come only if we invite him",
|> if I thought that even with an invitation, Tom might not come.

I certainly would say this.  For example, consider the context

    Bob will come if he learns of the party -- whether
    we want him to or not.  But Tom will come only if we
    invite him.

Since we haven't yet invited Tom, we of course have no idea of
whether he will in fact come (once he is invited) since,
for example, he may have a conflict, may want to avoid Bob, etc.

If you don't concede this (rather standard, I think) use of 'only if',
you have a lot of trouble straightforwardly expressing the thought
that Tom is the sort of fellow who won't attend in the absence of
an invitation.

I agree that it is sometimes (maybe even often) the case in English
that 'only if' is used in a context where 'if and only if' is implied,
but this does not remove its more fundamental meaning.  And I think
that you have picked a particularly bad example to illustrate the
point.
--
Gary H. Merrill  [Principal Systems Developer, C Compiler Development]
SAS Institute Inc. / SAS Campus Dr. / Cary, NC  27513 / [phone]
[e-mail] ... !mcnc!sas!sasghm