you don't know me

how do you know when you know someone? when you meet them? when you spend 58 days in a row with them? when you can predict their behavior? finish their sentences? list 35 or more facts about them? when you marry that person? when your last child (born and raised with that person) leaves for college? then do you know them? or what? i mean, i can talk myself into the idea that i don't really know anyone, regardless of the length of our relationship. or that i know people i haven't even met. right? so how do you know?