Panic: In economics, acute financial disturbance, such as widespread bank failures, feverish stock speculation followed by a market crash, or a climate of fear caused by economic crisis or the anticipation of such crisis.

— Britannica Online

Make no mistake — by this definition, what we’ve witnessed so far in 2008 is nothing less than a global market panic.

Acute financial disturbance? Freddie Mac and Fannie Mae imploded. Bear Stearns got rescued along with AIG ( NYSE: AIG ). but somehow Lehman Brothers wasn’t saved. Money markets broke the buck, and there was a formal bank run on IndyMac.

Feverish speculation followed by a crash? Our housing bubble fueled excessive borrowing and risky lending practices, resulting in the credit crisis we’re now dealing with. The S&P 500 is down 31% year to date, erasing the past five years of market gains.

Climate of fear? U.S. investor sentiment is at record lows. and the CBOE Volatility Index (the fear index) has posted all-time highs in recent days. No one seems to know where the next shoe will drop.

The list, sadly, could go on.

Don’t panic

Of course, no one wants to call this a market panic. Instead, in most places it’s been labeled a crisis. In fact, the term panic hasn’t been widely used to describe a market since the Panic of 1907 — which is unfortunate, because understanding this as a panic has something to teach us.

In the 19th century (the high time for market panics), Yale professor William Graham Sumner defined a panic as:

. a wave of emotion, apprehension, alarm. It is more or less irrational. It is superinduced upon a crisis, which is real and inevitable, but it exaggerates, conjures up possibilities, takes away courage and energy.

In other words, the subprime and credit mess is the crisis, and the panic is the exaggerations and doom-and-gloom language that come with it. We’ve seen plenty of that in recent months. Three of the world’s major financial publications have likened our current economy to the Great Depression more than 250 times so far this year. So please, let’s call this market by its proper name: the Panic of 2008.

Fortunately, a panic, Sumner continued, can be partly overcome by judicious reflection, by realization of the truth, and by measurement of facts.

Let us be judiciously reflective

So what do the panics of the early 20th century tell us about how we might overcome this one?

The last official panic — the Panic of 1907 — shook the U.S. economy to its core. Wall Street brokerages failed, depositors ran on banks, well-known companies went under, and the market’s liquidity was in question. (Sound familiar?) In this instance, J.P. Morgan and friends famously put together $25 million to keep the market afloat — a role now occupied by the Federal Reserve. By 1909, the Dow Jones index had more than recovered from pre-panic highs.

In 1914, the year the Great War began in Europe, the U.S. stock markets actually closed for nearly four months after foreign investors began pulling their money out of U.S. equities en masse to support the war effort. When it reopened, the market was devalued about 30%, but sustained rallies doubled that opening by the end of 1916.

Then, of course, came the Great Depression — the single most important economic event in U.S. history — which began with the Crash of 1929 and lasted arguably until the U.S. entered World War II in 1941. In 1932, unemployment hit 24.9%, and more than 9,000 banks failed during the 1930s. And there were no federally insured deposits until the Banking Act of 1933 created the FDIC, so when the bank failed, your money went with it. In fact, Wall Street’s very future — not to mention the economic model of capitalism — was in question.

For those investors who had both the money and the courage to invest in the 1930s, it paid off. One man famously borrowed money to buy 104 U.S. stocks trading for less than $1 a share in 1939. Talk about investing at the point of maximum pessimism! Four years later, though, his money had quadrupled. His name, of course, was John Templeton .

OK, what’s your point?

Judicious reflection, realization of the truth, and measurement of facts all say the same thing: We’ve seen markets like today’s before — and some far worse. And in every case, the point at which the market has turned irrational or overly pessimistic is precisely the time we long-term investors should have bought equities.

Despite the headlines proclaiming the next Great Depression, this is no Great Depression — only a panic helped along by the short-term mind-set of the financial industry. Financial media’s job is to attract readership by sensationalizing news events, and financial institutions, which are built on commissions and fees, want to keep money moving in and out in order to bulk up their own revenues. So both fan the flames of panic.

Individual investors like us do not have the advantage versus Wall Street when it comes to short-term trading, but we do have longer time horizons. Wall Street focuses on minutes, hours, and days, while we focus on years and decades. And that’s what makes their panics a good time for us to buy.

Let’s take the most modern example of market irrationality — the dot-com bubble and subsequent burst — and see what’s happened to some quality names since the S&P 500 was near its low in September 2002.