Why is the chicken-crossing-the-road joke funny?

Write this down on your palm so you don't forget: Humor is funny because of overlapping but conflicting frames of reference. There's no better way to say it.

Here's an example of a joke that is not funny:

Diner: Waiter, is this fly doing the backstroke in my soup?

Waiter: No, I think that's the breast stroke.

This isn't funny because there aren't two conflicting frames of reference. Both diner and waiter see what's happening in the soup and merely disagree on the swimming technique; their frames of reference remain identical. Thus we must rewrite the joke and have the diner ask what the fly is "doing" in the soup, expecting to find out how the bug got there, and then the waiter must employ a conflicting definition of "doing" and describe the fly's behavior at that very second -- "the backstroke."

Of course, if the waiter answered, "Floating on its back," it wouldn't be quite as funny. The extra humor comes from the thought of an insect engaged in a human-like swimming behavior, an inappropriate overlap of two worlds.

So, let's tweeze apart the subtle genius within the Henny Youngman riff "Take my wife ... please!" The sentence starts out as though "Take my wife" means "My wife is an example of this," but then suddenly, with the addition of "please!" we see that the speaker really means "Get this horrible shrew off my back."

Now the chicken joke. It has an internal conflict of an even more subtle nature. When we are asked the initial question we expect to hear a "punch line," which is to say, an actual joke, a twisting of contexts in the familiar humor pattern. Instead, we get a factual, lame, dull answer, the most straightforward response imaginable. So why is that funny? Because the non-joke is so wildly inappropriate to -- and thus conflicts with -- the joke format in which it is delivered. As our brain recognizes the conflict, our body responds with the twitching of 15 facial muscles, and our breathing is altered. This is laughter.

Why did the ancient Greeks think the gods lived on Mount Olympus, when anyone could have hiked up to the top and seen that no one was around?

As you go back in history, people get dumber and weirder. For example, back in the 8th century B.C. in Greece, there were wandering bands of Dionysian cultists who had a nasty habit of grabbing people, ripping them limb from limb and eating the various parts. It was like sushi without the little loaves of rice. Our point, however gratuitous and immature, is an important one: For most of human history we behaved like insects.

The Olympus stuff was first mentioned by Homer in "The Iliad," according to Robert Fagles, a Princeton professor who has just finished a new translation. (Among academics, the ultimate fantasy is to have some pointy-headed person quote Homer to you, and to be able to then reply, "That's fairly close, but actually I've done my own translation and ... .") Homer was the kind of person who, in addition to lacking a last name, liberally mixed myth and legend. Myth and legend are not synonymous. Greek legends were quasi-historical, like that business about the Trojan Horse, while myths discussed the (far-fetched) actions of gods, and represented through parable and metaphor more eternal truths. One shudders to think what those truths were supposed to be -- the male Greek gods were a bunch of misogynistic, boozing sleazoids who habitually commited rape, incest, castration, self-castration, and so on, while the female gods were vicious schemers and home-wreckers and Pandora-types who released evils over all Mankind.

Did the Greeks really believe this was literal truth? That's a 20th-century question: The Greeks didn't draw sharp distinctions between reality and myth. Plato and his fellow intellectuals knew that Zeus didn't really exist, but the average Greek citizen was less skeptical.

It stands to reason that some adventurers must have explored Olympus's peak in Homeric times. But even if they did, and found no gods at the top, they probably wouldn't have hopped up and down with indignation, because the gods didn't hang out at the summit permanently, just sometimes, and there were supposedly other places in the vicinity of Olympus where they set up housekeeping. Mount Olympus, at nearly 10,000 feet above sea level, is only the highest point of a longer range, much of which is shrouded in clouds. It looked like a place where gods would loiter. You'd be wary of stomping around in this realm of the gods.

"What happens if Zeus throws a thunderbolt at you?" asks Anthony Yu, professor of religion and literature at the University of Chicago. "Who the hell are you to want to go up there in the first place?"

The Mailbag

We received an anonymous letter asking simply, "Why is marijuana illegal?"

Dear dope fiend: Marijuana has been outlawed since the 1937 Marijuana Tax Act. You say you haven't paid your marijuana tax this year? Are you a dope fiend and a tax cheat?

The outlaw standing of marijuana is at least slightly the result of the labor situation during the Depression. There was much resentment in the southwest United States against Mexican immigrants taking farm jobs. Marijuana was considered a Mexican drug. Those crazy jazz musicians down in New Orleans smoked it, too. Middle America didn't like marijuana but, more than that, it didn't like the kind of people who smoked it. Scientists also were pretty sure it made people wacko and homicidal.

Marijuana remained legal even through Prohibition because, according to Yale historian David Musto, the legal community didn't think it would be constitutional to criminalize a weed. Outlawing pot would be like outlawing red ants.

The criminalization of machine guns made it possible to also ban marijuana. The Supreme Court ruled in 1937 that ultra-strict tax and license restrictions on automatic weapons were constitutional. Quickly, Congress passed the Marijuana Tax Act, which said you could not possess, barter, give or sell pot without a license and a transfer stamp. The government then refused to print up any such licenses or stamps.

One of the only groups that still was allowed to use the hemp plant legally was the birdseed industry, we are told. The marijuana seeds were famous for making the canaries sing terrifically.

The Marijuana Tax Act was replaced in 1970 by the Comprehensive Drug Abuse Act. Because of the new laws, some drugs are more illegal than others. Valium and other prescription medications are legally ranked as Class 3 drugs. Cocaine and morphine, which can only be prescribed under limited circumstances, are Class 2 drugs. Marijuana is a Class 1 drug. So is heroin. These drugs are limited to scientific experiments. (Tobacco, we would guess, is the No-Class drug.)