third from left

It could be any one of them.  

The person who makes the world-changing discovery.  The person who inspires others to explore.  The person who alters the course of human history.  It could be any one of them: third from left, second from right, back row, front row.  

Chances are, though, the impact they have on humanity will be small.  It could be every one of them.

The person who acts bravely and tries when he feels afraid.  The person who shows up when she is most needed, even though she feels tired.  The person who directs an angry feeling into something constructive.  It could be every one of them: second from left and third from right, front row and back row.

We should treat the people we meet thoughtfully and with dignity and respect, because it could be every one of them.  They are all valuable.