In the first place, what if a bookshelf is not supposed to bear much weight?
What if the whole object of a bookshelf is to not sustain beyond a certain number of pounds-per-inch?
In this case, the value of the bookshelf is its capacity for efficiency,
Or worse, emptiness.
This is similar to the architectural proviso of modernism,
the proviso for 'empty space, and nothing more!'
But this defies the purpose of a bookshelf, which is obviously to contain books.
Yet, the prescription is not one for heavy books specifically, unless the only goal is to physically
fill the bookshelf.
There must then be a spiritual prescription,
The prescription for appropriate literature.
But, if we said that the literature should be unseemly, steaming, or passionate,
that would defy the point of the ethical bookshelf in its specific mission.
One might say, perhaps the ethical bookshelf should contain only ethical books.
But, philosophically, ethical books raise a lot of questions about ethics that are
only ethical if they are answered satisfactorily.
So, in the sense of requiring ethical books, one should require ethical books of ANSWERS!
Yet, if ethical answers do, then one might as easily include answers of other kinds!
These other 'answer books' might provide answers on more practical subjects,
subjects that do not answer generally about all behavior, but instead give specifics
on how to act in certain cases, such as with carpentry or gluing.
But, now we are tempted to say that what is contained on the shelf is necessarily
non-fiction books, and the only criteria is that they provide 'answers'.
So, there should be some additional criteria which says that these books have some
special importance for the reader.
Either these books provide spiritual answers, or they provide just the right knowledge,
or they are books that for one reason or another are loved dearly.
There is then no definite criteria about the ethical bookshelf.
It is a shelf-of-books. It provides answers. Answers that are dearly loved.
Yet the books may be very light or very hefty.
They may be religious treatises or books about carpentry.
They may be picture books, novels, plays, cartoons, or summaries.
In short, anything may be required on the ethical bookshelf as long as it serves some purpose.
Specifically, the ethical purpose of the bookshelf is not even about whether the books are read.
They may serve an ethical purpose by being un-read, and therefore they may even be sinful books.
Or, they may be books that are referred to now-and-then. Aphorisms, precepts, and truisms.
The ethical bookshelf appears to be in one sense pragmatic, and in another sense illusory.
The books may be ephemera when the lesson is learned permanently, or when purposes are temporary.
The bookshelf becomes a particular place in the wilderness of civilization.
Particularly a place where the ethical purpose is manifest.