 Knowing a person is a matter of being acquainted with that person, and acquaintance involves some kind of perceptual relation to the person. What kind of perceptual relation? Clearly, not just any perceptual relation will do: I see and hear thousands of people while walking around a bustling city, but it doesn’t follow that I am acquainted with any of them. Must acquaintance involve an ability to distinguish that individual from others? It depends upon what such an ability amounts to. I am acquainted with my next door neighbor, even though, in some sense, I cannot distinguish him from his identical twin: if they were together I couldn’t tell who was who.