Given the text that you refer to,
it looks like simple crosstalk where using a phrase ■ one person thinks that
- “the group a is not exactly the same as group b”,
while the other person thinks that “a ■ b” means
- “the group a is not part of group b”.
For example, passage B,
is then interpreted as
Objector: If there are white horses, [then because the group of white horses is part of the group of horses] one cannot say that there are no horses. If one cannot say that there are no horses, doesn’t that mean that there are horses? How could it be that the [group of] white ones are not [part of the group of] horses?
Advocate: If one wants a [general unspecified kind of] horse, that extends to a yellow or black horse. But if one wants a white horse, that does not extend to a yellow or black horse. Suppose that a white horse were a horse [that the group of white horses were exactly the same as the group of horses]. Then what one wants [in each of the two cases] would be the same. If what one wants were the same, then a white horse would not differ from a horse [the group of white horses would be the same as the group of horses]. If what one wants does not differ, then how is it that a yellow or black horse is sometimes acceptable [for wanting any general horse] and sometimes unacceptable [for wanting a white horse]? It is clear that acceptable and unacceptable are mutually contrary. Hence, yellow and black horses are the same, [in that, if there yellow and black horses], one can respond that there are horses, but one cannot respond that there are white horses. Thus, it is evident that a white horse is not a horse [that the group of white horses is not the same as the group of horses].
A good way to think about this could be to think about groups (sets) as denoted by example objects, so that “A white horse is Spanish“ means “Any white horse is Spanish”.
If A sasy that “A white horse is Spanish“ and then B says that “No, a white horse is Portuguese.”, then they’re most likely not talking about two different arbitrary white horses, but about any white horse that one might choose.
However, the first passage, labeled A,
can not entirely be understood this way, because of the word “hence”. I suspect that something’s been lost in translation here.