smart joke

日曜日はジョークの日です。
"Pray, Mrs. Smith, why do you whip your children so often?"
"Mrs. Worthy, I do it for their enlightenment. I never whipped one of them in my life without making him acknowledge that it made him smart."
一年前に "smart"（http://blog.alc.co.jp/blog/3302827/108751） に "a kind of pain such as that caused by a wound or a burn or a sore" の意味もある事を知って "smarter" になったので上のジョークも直ぐに分かりました。