Is gold going to $6,300? Dylan Grice, an analyst with Societe Generale, says it’s possible, given the decline in central bank credibility. But investors need to keep one thing in mind: Gold is merely a vehicle to protect the purchasing power of money.

Gold is surging because investors see that the Federal Reserve — more concerned with deflation and unemployment than sound money — may be trapped in a never-ending cycle of monetary accommodation.

Ben Bernanke says he won’t monetize debt, but he already has. His Fed has bought $300 billion of Treasuries and is on pace to buy $1.45 trillion of government-backed mortgage debt all of which is being salted away indefinitely on the Fed’s balance sheet.

Why indefinitely? Because the Fed has no intention of unwinding its balance sheet so long as the economy is stressed. Witness comments this week from Bernanke, Fed Vice Chairman Don Kohn and San Francisco Fed President Janet Yellen all suggesting that the Fed’s “extended period” of low interest rates can be measured in years, not months. Today St. Louis Fed President James Bullard said rates aren’t going up till 2012.

So long as deficit spending continues, if the Fed wants to avoid deflation, it will be forced to monetize more debt.

[Elsewhere, capital controls are being erected in emerging economies like Brazil, Taiwan, and possibly Indonesia in order to keep speculative waters at bay. As Hong Kong’s chief executive remarked last week, a dollar carry trade spawned by low rates threatens to inflate dangerous asset bubbles in emerging markets the same way low Japanese rates did in the ’90s.]

Exploding debt throughout the developed world means other central banks face similar pressure.

(Click chart to enlarge in new window, reprinted with permission)

So confidence in paper currencies is waning.

Some people say it is absurd to buy gold; the metal has no intrinsic value. That may be. But is it any less absurd to hold paper? The best that can be said for paper is that if you lend or invest it, tomorrow someone will give you more paper in return. This is fine so long as its purchasing power is maintained. But it isn’t. A 2009 dollar is worth a 1914 nickel.

Eventually the value of all the paper you’ve accumulated goes to zero. The trick is to turn that paper into tangible assets with tangible value.

Gold may be volatile, but at least it maintains its real value:

(click chart to enlarge in new window, reprinted with permission)

Grice contends that the price of gold could reach $6,300 an ounce. He explains: “The U.S. owns nearly 263 million troy ounces of gold (the world’s biggest holder) while the Fed’s monetary base is $1.7 trillion. So the price of gold at which the U.S. dollar would be fully gold-backed is currently around $6,300. Gold is very cheap — at current prices, the USD is only 15 percent gold-backed.”

Absurd you say? It happened 30 years ago. President Nixon ended the Bretton Woods global monetary system and his compliant Fed Chairman Arthur Burns let inflation run wild. So by 1980 gold spiked to a level at which the dollar was “overbacked” according to Grice.

Did gold overshoot in 1980? Sure, but only because Paul Volcker was willing to hammer the economy to re-establish the Fed’s credibility. Today’s Fed has been very clear that it isn’t willing to put up with a recession of any kind in the service of sound money.

All of that said, investors should be careful. Grice’s chart shows that, over the long run, gold is likely to do no better than protect your purchasing power. An ounce of gold today buys a good men’s suit; in 100 years, it is likely to buy the same.

So gold won’t make you rich. But it may protect you from becoming poor.