It's often said that the best time to buy stocks is when everyone else is selling -- or sitting on the sidelines. That's when you get the best deals. So does that make stocks a good investment for you today?

No question, Americans are still wary of the stock market. The S&P 500 has remained within a narrow range for more than a year. Not surprising given the U.S. high unemployment rate and the fall in values of homes. On top of that, the world is jittery over the debt crisis in Europe, the possibility of inflation in China (even though China so far has not raised interest rates), and skirmishes taking place between North and South Korea. And then there are well-known economists such as Gary Shilling and David Rosenberg who are sounding alarm bells that now is not the time to invest in stocks.

Will Greece be able to pay an estimated €340 billion or $431 billion in debt in 2013, post intervention, up from the current €270 billion or $342 billion today?

The calculation here is that Greece, which is presently dependent on International Monetary Fund assistance to meet its obligations, will be able to do it, but it will be a close call.

Investors presently demand about 10.6% from Greece to borrow money for 10 years, while fellow eurozone nation Germany, obviously in a magnitude better fiscal position, pays 3.35%. In contrast, the United States pays just 2.56%.

Paraphrasing the great Mark Twain, if you don't like the stance of institutional investors, just wait a while.

Case in point: Investor sentiment toward the United States' large budget deficit and national debt.

A scant month ago, the talk was of bond vigilantes turning their wrath on the U.S., from Greece, Spain, Portugal and the rest of Europe's debt-plagued nations -- a predicament that would force interest rates up in the world's largest economy.

On the cusp of stress tests for Europe's banks, the continent may have already passed a major stress test -- one for the euro currency, Bloomberg News reported Thursday. A scant two months ago, the dominant concern among institutional investors was not the return on their investment in European government bonds, but the return of their investment.

Institutional investors drove up interest rates for debt-plagued nations Greece, Spain, Portugal, Italy, and Ireland, and banker-to-banker distrust increased.

The currency of the month in the foreign exchange -- the equivalent of the 'flavor of the month' in the currency markets? You guessed it -- the euro, which surged above $1.29 Thursday morning before pulling back slightly at mid-day.

The roughly 2-cent move higher Thursday continues a remarkable rebound for the European currency.

A month ago, the euro plunged to $1.16 amid a vortex of news that one or possibly all of Europe's debt-plagued countries -- Greece, Spain, Portugal, Ireland, and Italy -- could default. And there was even talk of a 'break-up of the euro-zone' and possibly an end to the euro.

Greece's debt woes this spring and talk of comparable problems in other debt-plagued eurozone nations, such as Spain, Italy and Portugal, had the euro bears talking euro-dollar parity as the euro plunged to $1.1877 in early June -- a four-year low.

But a month later the euro has strengthened 5.8% to $1.2574, and suddenly the teeth of the euro bears do not look as sharp.

The bond vigilantes -- primarily institutional investors who punish countries with a large deficit and/or problematic fiscal policies -- have made their presence felt in Europe. Just ask Greece. But will they make their presence felt on U.S. shores?

In the short-term, the answer appears to be no. "Central banks [including the U.S. Federal Reserve], by keeping rates near zero have basically covered the bond vigilantes in duct tape," economist Ed Yardeni told Bloomberg News. "We are not getting any votes of protest from the bond vigilantes in the U.S. because short-term rates are so low." Yardeni coined the 'bond vigilante' term in the 1980s.

At the G-20 summit in Toronto later this week, a battle may surface between the "immovable object" and the "irresistible force." Germany and the United States are at odds concerning the world's proper public policy stance at this stage of the financial crisis.

Germany is emphasizing that credit market and economic conditions are healthy enough to move forward with deficit reduction and related stimulus exit strategies, Bloomberg News reported Monday.

Thursday's good new data point comes from the International Monetary Fund, which said Greece's budget deficit reduction plan and economic overhaul appears to be on-track.

The IMF termed fiscal developments as "positive with central government revenue coming in closely as expected" and with expenditures under control.

The group also said pension reform has advanced and an agreement has been reached on many key parameters as outlined in the memorandum or understanding. Structural reforms are also progressing, including in the areas of local administration, privatization, labor market, and tax administration.

Japan's new prime minister, Naoto Kan, in his first major speech since taking office, said: "Japan is 'at risk of collapse' under its huge debt mountain."

For the past 20 years, Japan has been borrowing to keep its economy afloat. Most of Japan's bonds have been bought by Japanese citizens. Now with an aging population, Japanese citizens may not have the desire to purchase more bonds. The government would be forced to find other buyers who, most likely, would demand a higher yield.

Thursday's positive economic data point comes from International Monetary Fund Managing Director Dominique Strauss-Kahn, who views the European debt crisis as contained, and is still bullish regarding the global economic recovery.

Debt levels are a risk to growth, mainly in Europe, but authorities in the region "are now really committed to solve it" and "the problem has been contained" Strauss-Kahn said, Bloomberg News reported.

These days, theories regarding the euro's fate versus the dollar are flying through the air faster than commercial jets around New York's Kennedy Airport, so let's evaluate the major arguments.

On Wednesday at mid-day the euro strengthened about three-quarters of 1 cent versus the dollar to $1.2051.

A weakening euro. This stance argues that increased euro-zone government spending and/or monetary support for credit markets to help Europe's debt-plagued nations transition to sustainable fiscal policies will further dilute the euro's value versus the dollar. Essentially, this is the 'more euros in circulation' thesis, with a further weakening in the euro toward $1.10 seen; some forecasts even suggest a move toward parity, or €1 for $1.

Have the free economies of the world reached the limits of Keynesian economics?

That's the view of PIMCO's Anthony Crescenzi. Nations have reached a "Keynesian endpoint," Crescenzi wrote, in an e-mail note, Bloomberg News reported Tuesday. "Time, devaluations, and debt restructurings might be the only way out for many nations."

Keynesian economics refers to the policy advocated by economist John Maynard Keynes, who argued that fiscal stimulus is an effective tool to stimulate demand until business investment and consumer spending rebound.

The euro plunged versus the dollar again Friday, this time falling 1.2 cent to a four-year low of $1.2040.

Friday's culprit? Comments by French Prime Minister Francois Fillon that he's "not worried" about the current euro/dollar exchange rate, Bloomberg News reported Friday.

Fillion added that he saw only good news in a euro/dollar exchange rate at parity, or where €1 buys $1, Reuters reported Friday.

Just as the U.S. gets a grip on inflation, developments in Europe may tip the needle toward deflation, the New York Times reported.

Here's the scenario: Austerity measures imposed on Europe's debt-plagued government combine with a pull-back in consumer spending in Europe to take a substantial amount of demand out of the economy, putting downward pressure on prices.