Mutual fund manager Neil Hennessy believes in the bull market for stocks.

“I think the rally is for real,” he tells Bloomberg TV.

“You have to go back and look at what happened,” says Hennessy, head of Hennessy Funds. “In October, the financial system broke down. In November, the government injected $350 billion into the financial sector.”

Now, while economic and financial problems still exist, the improvement is impressive, he says.

“It’s sort of like breaking an ankle, just because you put a cast on it, it’s not going to be well the next day.”

Banks have stabilized, Hennessy notes. Their losses are shrinking, and they are raising significant new capital.

“You look back three, four months ago, and they weren’t able to sell any stock,” Hennessy points out. “That’s why the government was in. The financial sector is getting healthy, and investors know it.”

Bottom line: “The deleveraging of this system is going to be good for the long-term,” Hennessy says.

That’s because it allows “sustained growth, not the growth we saw at the end of the 1990s and the end of 2007, which was highly leveraged growth.”

Others are more skeptical. “I'm thinking that unfortunately the world economic situation is precarious now, and I'm worried about this recession," Yale University economist Robert Shiller tells the Financial Times.

“I still see this as likely to be … a period of disappointing economic performance for some years.”