A U.S. industrial renaissance is fueling a strong equity bull market, but it's going unrecognized because fear and uncertainty have gripped the markets, says Richard Bernstein.

And, he notes, that's a good thing from an investment advisor’s perspective.

"When's the last time a bull market has started when investors are certain?" Bernstein of Richard Bernstein Advisors asked an audience at an Investment Management Consultants Association (IMCA) conference in New York City this morning.

The message by Bernstein was that advisors need to look at the mass level of concern, much of it based more on perception than reality, as an opportunity. Conversely, he noted that a time to be cautious is when the market seems is lockstep in the optimistic pursuit of the hot investmen such as the dot.coms in the 1990s.

"The time you should worry is when people are certain," he said.

Bernstein told a ballroom full of advisors that the U.S. is in the midst of what will probably turn out to be the biggest bull market of their careers—one which in some ways mirrors the bull markets of the 1980s and 1990s.

A characteristic off all these bull markets is that investors were late to recognize they were happening, he said.

“You have to remember that bull markets are periods of fear and uncertainty,” he said. “They’re not periods of wine and roses.”

Bernstein, who served as Merrill Lynch’s chief investment strategist for more than 20 years, said the U.S. is four years into an equity bull market that resulted in 100% growth. Among the driving factors were the resurgent growth among small- and mid-cap U.S. industrial companies that have benefited from compressed wages and cheap energy prices.

“The U.S., outside of the Middle East, has the cheapest gas prices in the world,” he noted.