Wow , you two make it really hard for another to follow your conversation .. not to mention your points...
Miguel, in my opinion there are no two things/objects... what ever you want to think of .. equal (as in "the same") .. but in order to distinguish between two "of the above" that LOOK the same/equal one would have to be all-knowing... to be, in a word, "God"
I agree with Y-san, "sameness" as you two call it is a concept that appeared out of necessity : to learn, to generalize, to be able to share at least the part of the information that one knows and wants to share.. Most people learn best and understood things by comparison to a familiar thing/object.
To use your example :If you say "pony" is the same as a "horse" but with a smaller caliber/height , does this mean that ponies are 99.99% equal to a horse, except height ? NO, because not event two horses are not equal..not by a long shot... you cannot have two identical things/objects, but they might be enough alike to be recognized by most as belonging to a "same" something (class, order, etc..).