Final answer:
The principle behind the argument against destroying books is best represented by the perspective that we have a moral duty to not destroy potential sources of future enrichment, which coincides with themes in environmental ethics and conservation.
Step-by-step explanation:
The principle underlying the argument that we have a moral obligation not to destroy books for the sake of future generations is most accurately expressed by option (D): "We are morally obligated not to destroy anything that will most likely enrich, either intellectually or emotionally, our posterity." This choice aligns with the concept that our actions should aim to benefit future generations, akin to our obligations in environmental ethics and conservation. These ideologies are grounded on the anthropocentric view that while human interests are at the forefront, they encompass a responsibility to ensure the sustainability of resources for coming generations. As the environmental ethicists suggest, our moral responsibilities today should be judged by their impact on the future, ensuring that we balance our present actions with the potential to improve the lives of those who will inherit the Earth.