It should be pointed out that the meaning of the word "single" is far more than what we use here. A paper only involves one topic, which is completely opposite to the History of XXX or a manual or an encyclopedia. In this sense, the theme of "upside down world" of medieval writers should also be a single theme. Many writers are involved, but they all revolve around a specific theme (from their imaginary assumptions to examples, paradoxes and fables, such as fish flying in the sky and birds swimming in the water). It seems that this is an ideal single theme. But in fact, in order to write such a paper, we need to discuss all the authors related to this topic, especially those unknown authors who are not recognized. Therefore, this topic should still be classified as "a comprehensive paper with a single theme", which is more difficult to write and needs to prepare countless materials. If someone must write it, I suggest that the title be changed to "The Theme of' Inverted World' by Carolyn Dynasty Poets". As soon as the scope is narrowed, we will know where to find materials and where not to find materials.
Of course, comprehensive papers are more energetic to write. After all, it is boring to spend a year or two or even longer studying a writer. However, we must understand that writing a paper with multiple choices in a strict sense does not mean that we can't do everything from a perspective. Writing a paper on Aldecoa's novels requires us to have a deep understanding of Spanish realism, we also need to read Sanchez Phil rossio or Garcí a Oltra, and we need to study Aldecoa's American novels and classical literature. Only by putting the author in the panorama can we understand and interpret him. But using panorama as background and painting panorama are two different things. The former only painted a portrait of a knight with fields and rivers as the background, while the latter painted many fields, valleys and rivers. We must change the technology, or in photographic terms, change the focal length. The panorama shot from a single author's perspective is a bit out of focus, incomplete and inferior.