[Note: I wrote this while we were lazing around in a rented cabin inland from the north shore of Lake Superior. I noticed on a map that we weren't too far from a body of water named "Devil Track Lake," providing me with the metaphor in the second paragraph]

Other tree-huggers fret about the disappearance of the Snail Darter in some minor tributary, while I worry about the smallpox virus. It's imprisoned in suspended animation only in two deep-freeze chambers, in Georgia (U.S.) and in Moscow (Russia). The World Health Organization is meeting this month to decide whether or not to pull the plugs on them. Fools! It doesn't cost much to save the virus, and you never know when you're going to need it. Doesn't anyone remember H.G. Wells's The War of the Worlds, where the interplanetary invaders died of measles?

We must fight the battle against infectious diseases because any prey animal must try to avoid a predator, but we can never win the battle. Nature requires that all ecological niches be always filled, including the ones where we're the victims. Population pressure requires some premature deaths -- we can't all reproduce and we can't all live to threescore and ten. The earth won't stand it. As Malthus said, we need both pestilence and war. A military historian wrote in a recent New York Times Book Review article that the purpose of the state is to mount war on other states. If the state is incapable of making war, it must be carried out by smaller units such as ethnic groups, social classes, economic classes, or even towns. No matter how much we claim to worship God we must follow the Devil Track. Shakespeare put it a little more elegantly in King Lear (Act IV, Scene II):

Humanity must perforce prey on itself,
Like monsters of the deep.

Edward Jenner is credited with inventing inoculation. He noticed that milkmaids never got smallpox. They got mild cowpox instead. Without understanding anything about microbes, he put his observations to practical use by vaccinating everyone in sight with cowpox ooze. Sure enough, it worked -- so well that smallpox is on its way to extinction. But the original intent was not to eliminate smallpox but to produce a mild disease in the patient that would protect against a more serious disease. That's simply a variant of the idea to use a lesser evil to combat a greater evil.

Vaccination would not have lived beyond Jenner, would not have even occurred to Jenner, if that mental model were not already in place. This concept, which still lives on in homeopathic medicine, was popular among 18^th and 19^th century doctors. Most ailments were treated with mercury, arsenic or lead compounds that, if taken in larger amounts, led to a painful death. All these compounds, in small doses, collect in the liver and cause diseases that happen only after a lifetime of taking them. There's no way to tell how many people died of the cures because the effect was so slow. The treatments were effective, however, because the mechanism was believed in and well-understood by the doctors.

No invention or discovery can be made that doesn't fit in with a general idea that's already around. A discovery has to make sense to others in order to remain a discovery. As a society, for example, we're trying hard to believe in outer-space aliens, but we can't really conceive them, because then we'd take the sighting reports seriously. If an alien actually appeared, most people would interpret it as a miraculous apparition of the Virgin Mary. Thousands would rush to the spot hoping for a glimpse of the Mother of God. That's because, as in the 14^th century, we don't really need aliens but we do need Mary.

The concept of pitting the lesser evil against the greater evil is as old as the Blessed Virgin Mary and her foremothers. A famous mythic example is Mithridates, King of Pontus. As a young king, he understood that the main talent he needed to become an old king was to avoid being poisoned. He consulted experts on the poisons popular among members of his court. He even had to watch out for his mother. She had already rid the kingdom of some relatives who stood between her and the levers of power. He took small amounts of the poisons, gradually increasing them until he was no longer susceptible to ordinary fatal doses. He survived into old age, although perhaps he didn't feel well.

I can think of two methods by which the Mithridates technique might have worked. His body may have built up tolerance to poisons the way it tolerates ever larger doses of nicotine or opiates. Conversely, he might have built up sensitivity, as with allergies, so he would throw up any poisoned food before it could be absorbed by the body. Either way, it involved a lesser evil warding off a greater evil.

If you catch smallpox nowadays, it's bad for you as an individual, but not necessarily bad for the human race. Hans Zissner's Rats, Lice and History explicates this theme at length, describing how host and parasite must evolve into a symbiotic relationship over time, until they are one organism, host and parasite indistinguishable. He uses syphilis as an example, which, even before modern treatment, had become chronic rather than acute. It was taking longer and longer to kill its victims, who were becoming tolerant.

We've lost that idea. With our new powers, we're convinced that we and God, working together, can actually eliminate evil, not just learn to live with it. We're going to eliminate crime by eliminating the criminal; Wipe out drugs; wipe out cigarettes; wipe out the evil Haitians and the Bosnian Serbs; bring peace through warfare. Onward, Christian Soldiers! We'll just decide what's evil and go out and destroy it. If smallpox is on Satan's side, smallpox has to go, and then we'll have Satan on the run. But Satan is the Lord of the World. When Satan tempted Christ, he took him to the top of the world and, among other things, offered him domination over everything. Christ refused.

An engineer who was caught in the last layoff at the company where I work was one of several born-again Christians who work there. He has other problems as well: his wife divorced him and he's having trouble finding a good Christian woman to replace her. He's still in touch with other Christians at work, though. One of them told me that, a few weeks ago, two or three of them met the layoffed guy for lunch to counsel and strengthen him. They did this because he had admitted to one of them that he was getting so hard up he was tempted to visit a prostitute, or, worse yet, to masturbate. They all ganged up on him, prayed with him, encouraged him to just say NO to the temptations of the flesh. But it seems obvious to me that the main reason those tele-evangelists get into trouble with sex is because they don't inoculate themselves with small sins, do not choose masturbation over the cute little naive church secretary who's so pure you can't resist her.

Similarly, without smallpox, what are we going to do if cowpox raises the ante and forms a virulent mutation that's too tough even for smallpox vaccine? If we understood that evils are relative, we might wish we still had smallpox as an inoculation against something much worse. We already wish we still had the USSR, who protected us from the Serbians. And we'll most certainly need masturbation to deliver us from evil.

Note added January 2007: I ran across another example of this principle in an article, "Why We Develop Food Allergies," by Per Brandtzaeg in the January-February 2007 issue of American Scientist (Vol. 95, #1, p. 34). In discussing evidence for the beneficial effects of some soil bacteria, the author writes:
"...This evidence supports the extended hygiene hypothesis, which argues that a too-hygenic lifestyle in industrialized countries can prevent the mucosal immune system from maturing, leading to inadequate secretory immunity and fewer regulatory-T cells."