Conditional imperfection

Neal Whitman nwhitman at AMERITECH.NET
Thu Nov 21 04:50:13 UTC 2013

 From my latest blog post:

    "You're a Jew," Doug said, "if and only if you believe in God!"

    "So ... Muslims are Jews?" I asked.

    "No, Dad," Doug explained. He then summarized for me the concept of
    /only if/, concluding, "You've out-literaled yourself!"

    Later on, I drew a truth table for /if/ and one for /only if/, and
    showed them to Doug. He found that, after all, he and I agreed about
    the meaning of /only if/. So what's the difference between /only if/
    and /if and only if/, I asked.

    "I don't think there is one," Doug said.

    I drew up the table for /if and only if/, and Doug understood it,
    but in his opinion, in ordinary conversation, /if and only if/ was
    just an emphatic way of saying "only if".

    "I'm with Doug on this one," my wife offered. In a casual,
    dinner-table conversation, I shouldn't have taken Doug's /if and
    only if/ in this technical sense.

    Technical sense? This was my first inkling that there was more than
    one sense!

Is this new to anyone else?


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