You could say Charles Plosser is excited about being president of the Federal Reserve Bank of Philadelphia. Or you could say he's feeling engaged, challenged, and generally optimistic overall.

But you can't say he's comfortable.

His discomfort stems from the current level of inflation - specifically the "core" rate that Fed officials rely on to gauge their effectiveness as guardians of the nation's monetary stability. During 2006, core inflation clocked in at 2.8 percent, and while that's pretty tame compared with some eras we can recall (think the 1970s), it's a bit too high for people who consider themselves hard-core inflation-fighters, as Plosser does.

But how much is "a bit"? How far would inflation have to fall to be inside what Fed-watchers call the "comfort zone"? Plosser won't say.

"I haven't given my comfort zone. I'm not going to reveal it," he told me in an interview last week. He does, however, stand by remarks he made last fall as part of his first public speech since becoming Philadelphia Fed president in August:

"At that time, core inflation was running about 2.5 percent. That's higher than I'd like to see it.' "

There's more to this than simple academic musing. Being president of the Philadelphia Fed makes Plosser a member of the Federal Reserve's key Open Market Committee, which sets the course for U.S. interest rates - and, to some extent, the pace of the overall economy.

Although Plosser won't actually cast a vote on interest rates until 2008 - voting power rotates among the regional Fed presidents - his voice will be heard whenever the panel meets in Washington. Already, some professional Fed-watchers have called Plosser among the most hawkish - that is, the least inflation-tolerant - of all the central bank's key players.

"Certainly, I'm not a fan of inflation," Plosser told me.

The thing is, "there's only one institution in our government that has the ability to control inflation. That's the Federal Reserve. So I think it's important that the central bank take that charge very seriously."

How seriously is a question we could see play out later this year.

Analysts and financial markets are divided over the outlook, with some saying the economy has slowed enough to justify a Fed rate cut, while others believe rates will stay firm or even rise.

The key, however, is how Fed officials themselves see it. And since their deliberations are never public - minutes of the central committee meetings are released long afterward - Fed-watchers pick over officials' public statements intently for signs of what's to come.

That could change. One idea being debated among Fed officials is to introduce an explicit target for inflation. Then, if prices were rising faster than the target rate, investors and business planners would know to expect an increase in short-term interest rates.

Former Fed Chairman Alan Greenspan opposed the idea during his 18-year tenure, which ended in February 2006, arguing that the bank needed the discretion to deal with changing economic conditions. But Plosser, among others, questions whether that's appropriate for a post-Greenspan Fed.

"You can't take issue with [Greenspan's] success," he said.

But, he added, "there's no little black book in the upper-right-hand corner of the desk drawer that tells you how you make monetary policy like Alan Greenspan."

Ben S. Bernanke, Greenspan's successor, has endorsed naming an inflation target, and Plosser supports the idea "as a philosophical statement." But getting such a change through the Fed's cautious bureaucracy might take some time.

Meanwhile, there's plenty to keep Plosser busy here in Philadelphia. The regional Fed is one of the biggest financial institutions in town, with 1,100 employees and a charge to oversee local banks throughout eastern Pennsylvania, southern New Jersey, and all of Delaware.

An Alabama native, Plosser spent 28 years at the University of Rochester while that Upstate New York city's fortunes turned down dramatically. Eastman Kodak Co., for example, had 50,000 workers there when Plosser arrived but just 10,000 when he left.

While Philadelphia has "a wealth of talent," he said, some of the issues here are similar. "One of the things many older communities face is, how do you promote and retain talented individuals?" Plosser said.