That texts are unique is simply an objective fact. As soon as you change just one letter, you have a new text with 'difference'. I'm saying this is not a useful perspective because it only gets interesting when you can point out what kind of difference there is and why it is important, and then you end up with something that higher quality texts may have in common.
While critics may have some difficulty telling authors or texts apart because of human limitations, computers attain very high accuracies with various authorship attribution methods. This underscores my point: if you focus on differences, you will end up identifying very particular things such as a particular author or even the style of a particular work, that's just the idea taken to its extreme.
On the other hand, I believe that the quality of a work, which is one kind of value indeed, can lie in commonalities instead of differences. I don't have a concrete example, but from reading literature I do get the feeling that there is something definite that they share. I don't mean something on the level of a trope, that would be too superficial. I think it's OK to admit that we don't know, but not a good idea to preclude it from being described as part of a taxonomy because it's supposedly only about differences. There's simply too much difference in all the unique things around us for that to be informative.
While critics may have some difficulty telling authors or texts apart because of human limitations, computers attain very high accuracies with various authorship attribution methods. This underscores my point: if you focus on differences, you will end up identifying very particular things such as a particular author or even the style of a particular work, that's just the idea taken to its extreme.
On the other hand, I believe that the quality of a work, which is one kind of value indeed, can lie in commonalities instead of differences. I don't have a concrete example, but from reading literature I do get the feeling that there is something definite that they share. I don't mean something on the level of a trope, that would be too superficial. I think it's OK to admit that we don't know, but not a good idea to preclude it from being described as part of a taxonomy because it's supposedly only about differences. There's simply too much difference in all the unique things around us for that to be informative.