(FORTUNE Magazine) – Friends, are you troubled by stock valuations that make no sense? By market moves so violent they tie your stomach in knots? By an economy that willfully defies every rule you ever learned?

Well, untrouble yourselves and worry no more. You may think we live in revolutionary times, with stunning new technologies taking us places we've never been. I'm happy to report that nothing could be further from the truth. Fact is, we've been here before--many times. You see, the markets, the economy, indeed the whole world moves according to predictable cycles. Simply study them, and you'll realize that the future isn't a mystery at all. It's preordained, an open book waiting to be read.

How am I doing? Are you buying any of this? Frankly, I didn't think so, but if you visit the Web, you'll find such stuff alive and well. For an entertaining break in your day, go to a search engine and type in "Kondratieff wave" or "Elliott wave" or, for even lighter fare, "Donald A. Bradley" (he thought stock prices were determined by the planets). In our extraordinary times you might have thought these deterministic wave theories would have finally died out. But they haven't (though it's always been impossible to count their followers)--and their stubborn survival against the odds may even hold a message.

Most people haven't heard about this brand of voodoo since Robert Prechter, high priest of the Elliott wave, was lionized for calling the stock run-up that began in 1982 and the crash of 1987. Since then his big-picture forecasts have been laughably terrible, with global economic depression continually just around the corner and the Dow headed below 1000. His famous newsletter, The Elliott Wave Theorist, recently gave up financial forecasting in favor of broader societal issues, for which the outlook is also very grave but at least not subject to embarrassing comparisons with index numbers. (He does still venture market calls in a smaller, niche publication.)

The Elliott theory falls at about the midpoint of wave looniness. Toward the more respectable end is the Kondratieff wave, a fairly modest attempt by an obscure Russian economist to chart 54-year cycles in certain aspects of the industrial economy during the early industrial age; disciples have turned it into a ludicrously complex "tool" for trading oat futures, among many other uses. Toward the spectrum's other end--before we get to the planets--are nameless techniques built on the Fibonacci sequence, fractals, groups of five, groups of nine, and other supposed patterns with one thing in common: Their proponents have no idea why they should work.

Of course the results are pathetic. From long-range economic forecasts to predictions of the next week's market moves, these "theoreticians" might as well be reading tea leaves. At least they can be entertaining. Thanks to the Web, you can drop in on debates of theological intensity about whether the market's "correction" wave is always longer than the "impulse" wave--or whether the 1949-66 impulse was 6,084 days, while the 1966-82 correction was in fact only 6,025 days! You can catch up on uses of the Swing Oscillator--"particularly useful for avoiding miscounting a subdivided wave 3 as a wave 5." You'll find many statements noting with deep significance that, for example, "this week's high was within a whisker of being a 61.8% retracement of the 1996-99 bear move." Many of the analysts get excited by the number 1.618, which is actually quite an interesting number for mathematical reasons, but why it should exert mysterious power over prices of stocks, bonds, gold, and soybeans is a mystery to me--and, I would think, to anyone with an eighth of a brain.

Excuse me. That was harsh. It's clear that many devotees of wave theories have a lot of intelligence. They've been led into folly by a powerful need, which we all feel, to impose order on the world. The apparent craziness of today's economies and markets, while seemingly a rebuke to wave theories, also amplifies their appeal. That's why this nonsense is worth bringing up just now: When you can't make sense of things any other way, there's a lot of allure in believing that they've all happened before, that this is just another turn of a giant wheel.

If only it were true.