"No tiene por qué + inf

Question

I recently read the following (Mexican Spanish):

–No obstante, una cosa no tiene por qué impedir la otra.

"No problem, one thing doesn't have to interfere with the other."

My question is the addition of por between tener and qué. I believe it is used for emphasis... no tiene por qué impedir...

Are there guidelines for when you would use this construction? Can it be used in both a negative and affirmative construction? Or am I right in thinking that it doesn't make sense to say:

Tengo por qué buscar un libro.

but it could make sense to say:

No tengo por qué buscar un libro, as in, I don't have to look for a book.

Thank you,

J

You are right! - cogumela, Sep 22, 2010

Gracias Cogumela :) - Jeremias, Sep 22, 2010

Answer 1

This is a very long workaround, but try this:

Una cosa no tiene (razón alguna para justificar) por qué impedir la otra.

One thing has no (reason at all to justify) why preventing the other.

Si hace sentido, gracias. - Jeremias, Sep 22, 2010

Answer 2

I can understand your doubt.

Por qué here significa " ningún motivo para"

so, in the afirmative sentence is not correct it would be tengo que buscar un libro, or better, tengo motivos para buscar un libro.

Maybe this link can help you.

[http://spanish.about.com/od/writtenspanish/a/porque.htm][1]

You stated it much more clearly than I. - 0074b507, Sep 22, 2010

Answer 3

The por gives it a sense of "the reason for" or motive, does it not?

No tengo por qué buscar un libro. I don't have a reason for searching for a book. (or you can look at it as por qué [porqué] I don't have a why for looking for a book.

I don't think that this is the periphrasis tener que but rather the periphrasis por qué as in No tengo el porqué.