History
The social studies teacher had just finished a unit on war and peace. "How many of you," he asked, "would say you're opposed to war?"
Not surprisingly, all hands went up.
The teacher asked, "Who'll give us a reason for being opposed to war?"
A bored-looking boy in the back of the room raised his hand.
"Johnny?" the teacher prompted.
"I hate war," Johnny said, "because wars make history, and I hate history."