At the unspoken urging of Joseph Lewis -- a billionaire multiple times over -- investors are wondering whether beat-up investment bank Bear Stearns (NYSE:BSC) is worth a second look. The British-born Lewis, who now resides in the Bahamas, made a good part of his fortune making savvy bets on currencies, and was the founder of the Tavistock Group, an investment company that holds stakes in more than 170 companies, ranging from resort properties to sports teams.

Lewis' $860 million stake makes him the single largest Bear Stearns shareholder, ahead of Putnam Investment Management, Private Capital Management (a unit of Legg Mason (NYSE:LM)), and Bear's CEO Jimmy Cayne. While Lewis finally had to disclose his stake, his buying has come over the past few months, as Bear has been troubled by turbulent credit markets and some highly publicized implosions at a few of its hedge funds. Since early 2007, Bear's stock has dropped more than 35% and now trades at 1.2 times its stated book value in late May.

The five-million-dollar question is why Lewis would make such a bold move. One thing you can immediately cross off your checklist is publicity. Lewis was once quoted as saying "I really feel that if one is successful, one of the rewards of your success is the quiet enjoyment of it. Being on the front page of newspapers doesn't allow that." To emphasize that statement, he hasn't granted a public interview since 1998.

The next option might be that Lewis has designs on being aggressive and shaking things up at Bear. While those used to the headlines made by activist shareholders like Carl Icahn may jump at this idea, it seems unlikely. In the mid-1990s, Lewis took a major stake in Christie's auction house, but it doesn't appear that he took an active role at the company. That he would step out of his mold and prod Bear a bit isn't out of the question, though it seems unlikely.

So what are we left with? That's right: Maybe Joe Lewis thinks that Bear's stock is simply a great value right now and a great place to invest $860 million.

What's interesting for investors here is that because of the low profile that Lewis keeps, the announcement of his stake in Bear hasn't sent the stock skyrocketing in the same way it might if, say, Berkshire's (NYSE:BRK-A) (NYSE:BRK-B) Warren Buffett started buying aggressively. Using Lewis' SEC filing, I was able to figure that the average price of the Bear stock that he's holding is right around $106 a stub, a measly 2% lower than the stock's price as of this writing.

Unfortunately, I don't have a direct pipeline into Mr. Lewis' thought process, so I can't say, in particular, what it is that he likes about Bear's stock -- though I have a hunch that the price has a lot to do with it. There is a chorus out there right now (a chorus that I've contributed to) saying that, over the near term, investment banks could face some softer times. But, similar to some of the other large, quality investment banks like Goldman Sachs (NYSE:GS) and Morgan Stanley (NYSE:MS), Bear seems well-positioned to be a solid business over the longer term.

Bear is scheduled to report its third-quarter earnings on Thursday, Sept. 20, so investors should get more color then about how Bear has been handling the turmoil. Consensus analyst estimates have the bank's earnings per share declining nearly 40% from last year, though the estimates range from Bear topping last year's numbers on one end to sliding more than 65% on the other.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. The Fool's disclosure policy has never once been caught with its pants down. Of course, it doesn't actually wear pants ...