In Spanish double negatives are valid when referring to the absence of people and things.
“No hay nada,” — literally, “there isn’t nothing” — is a multi-purpose expression which can mean the fridge is empty, no one showed up for the game, or nobody knows anything about this. It can also mean “there’s nothing.”
Likewise, “no hay nadie” means there’s no one, and “no tenemos nada,” means we have nothing.
There are some people, however, usually among those more given to scientific than artistic pursuits, who will insist that this is all wrong, that a double negative is a positive, and that the correct way to deny the existence of something or anything is “no hay algo.”
This isn’t only anathema to those sensitive to the aesthetic qualities of the language and appreciative of its simplicity (not its economy), but also confusing. They can’t tell if the person arguing thus is merely trying to drum up some controversy for conversation’s sake, or is really incapable of grasping the literary equivalent of two-plus-two.
There is a way to avoid the double negative without causing the poet to pack it all in and get a job, and that’s by inverting the object and the verb.
So the lie, “no temo nada,” – I fear nothing – can be “nada temo” keeping both sides happy, although I’m afraid it might get a bit monotonous.