Do Not Litter And Feed The Birds

A sentence in natural language can often be interpreted in two ways, but in mathematics, we must be precise in our use of language and avoid ambiguity. This often least to humorous interpretations of street signs and the results can be adorable.

Take this street sign example, which I photographed in September of 2010 at the Happy Paws pet store near NYU. It’s a wonderful sign on a messy street that immediately attracted my attention and confusion.

Do Not Litter And Feed The Birds

Please leave a comment below on how you understand this sign:

A) Two separate commands: you should not litter AND you should feed the birds. Why?

B) You should neither litter nor feed the birds. Why?

C) You should either not litter or not feed the birds, or do neither. Why?

D) All of the above (and why?)

E) Explain a distinct interpretation.






3 responses to “Do Not Litter And Feed The Birds”

  1. benblumsmith Avatar

    I can get all these readings, but actually I think the most natural reading for me is in the (E) category:

    "If you litter, you will be feeding the birds, and this is no good, so don't litter."

    It's amazing how much propositional (both descriptive and normative) content I'm getting out of a sentence that is formally an imperative:

    a) "If you litter, this will feed the birds" (Descriptive proposition.)

    b) "This would be bad." (Normative proposition.)

    c) "So don't do it." (Imperative.)

    … but even though this is the most natural reading for me, it's still unsatisfying. What's wrong with feeding birds?

  2. cheesemonkeysf Avatar

    I love these instances of what contemporary rhetorical theorists call the aporia (from the Greek) for that gap which sometimes opens up between intention and delivered or received message.

    My own favorite example of this slippage of language comes from a sign on the Via Chiantigiana (the Chianti Road in Tuscany's Chianti country) at a woodland turn=off on the road.

    Two signs, the ostensibly translated English version above that requests, "Speak Slouly Please" and the probable Italian intention, asking "Parlare a bassa voce," meaning "Speak quietly please."

    An obvious gap between intended signified and actual imperative, yet one in which the stakes are in fact extremely low.

    Still, there is delight to be taken in our inherent human fallibility. In the (translated) words of the old Yiddish proverb, "Man thinks, God laughs."

    – Elizabeth (aka @cheesemonkeysf on Twitter)

  3. Zeno Avatar

    I see littering and birdfeeding as one act, so littering is fine as long as it's not accompanied by birdfeeding.