Hello prospective translators,

I am working on creating a custom 'ex libris' stamp for myself because
I lose too many books to friends.  I'm a philosophy student and there
is a quote from Milan Kundera that I have long been enamored with
because it encapsulates my approach to philosophy as a discipline.  I
want to incorporate it somehow into the stamp design.  Here is the
quote:
"Only the most naive of questions are truly 
serious ... It is questions with no answers
that set the limits of human possibilities,
describe the boundaries of human existence."

I would like to include a Latin version of the four word phrase
"Questions with no answers" on my stamp.  Given the context of the
phrase, what is the best translation of it?

Hello.

I'd go with:

"Quaestiones sine responsis."


Breaking it down:

quaestio (noun)- inquiry, question
http://www.etymonline.com/index.php?l=q&p=1
This is a third declension noun so the nominative plural would be "quaestiones."

sine (preposition + ablative) - without 
http://www.jact.org/subjects/vocablist.htm

"Sine" is the best preposition to convey the meaning of "with no."

responsum (noun) - answer
://www.google.com/search?hl=en&lr=&safe=off&q=responsum+answer&btnG=Search
This is a second declension neuter noun, so the plural ablative would
be "responsis."

The phrase "questions and answers" may be translated as "quaestiones
et responsa." Examples of this usage:
://www.google.com/search?hl=en&lr=&safe=off&q=%22quaestiones+et+responsa&btnG=Search

Here, however, the preposition "sine" (without) requires "answers" to
take the ablative form.  Thus, we use "responsis."

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search strategy:
My own knowledge of Latin plus the searches mentioned above.

I hope this helps.