NEW YORK - July 2, 2010 - With the stock market lurching again, plenty of investors are nervous, and some are downright bearish. Then there’s Robert Prechter, the market forecaster and social theorist, who is in another league entirely.

Prechter is convinced that we have entered a market decline of staggering proportions - perhaps the biggest of the last 300 years.

In a series of phone conversations and e-mail exchanges last week, he said that no other forecaster was likely to accept his reasoning, which is based on his version of the Elliott Wave theory - a technical approach to market analysis that he embraces with evangelical fervor.

Originating in the writings of Ralph Nelson Elliott, an obscure accountant who found repetitive patterns, or “fractals,” in the stock market of the 1930s and 1940s, the theory suggests that an epic downswing is underway, Prechter said. But he argued that even skeptical investors should take his advice seriously.

“I’m saying, ‘Winter is coming. Buy a coat,’” he said. “Other people are advising people to stay naked. If I’m wrong, you’re not hurt. If they’re wrong, you’re dead. It’s pretty benign advice to opt for safety for a while.”

His advice: individual investors should move completely out of the market and hold cash and cash equivalents, like Treasury bills, for years to come. For traders with a fair amount of skill and willingness to embrace risk, he suggests other alternatives, like shorting the market or making bets on volatility. But ultimately, “the decline will lead to one of the best investment opportunities ever,” he said.