From a conversation yesterday between me and my 8 year old son Zane:
Z: What did you just take a picture of?
B: That cloud up there.
Z: But what's so special about that cloud?
B: It doesn't look like any other cloud. That cloud is going to disappear and no other cloud will ever be like it.
Z: But there are thousands of clouds. Another one will come along as soon as that one disappears and you could photograph it instead.
B: It wouldn't be the same cloud.
Z: So that one is different? What does it look like that makes you want to take its picture?
B: It looks like itself. Make sense?
Z: Not really. Can we go to practice now?