That person over there. He looks like someone from your fifth grade elementary school class, but older. Is he that person? How would you find out? What can you tell from just observation?
Suppose, when you ask him, he says he is your fifth grade classmate and excuses himself from further conversation because he is in a hurry. Would you be satisfied that you have identified him?
Suppose, instead of walking away, he says he has lost his wallet and asks to borrow some money to buy a train ticket home. Are you willing to lend him $20? How about $200? Are you still feeling good about his identity? Would you ask any further questions?
Is every watch a Rollex? Is every Picasso an original? Is every “friend” a real friend?
What makes things the same? Or different? Is every difference significant? How do you judge that? Where do we learn such things? Does schooling improve the process?
To examine these issues further, see The Things We Recognize