Some of the best companies in the world currently trade for around 10 times forward earnings -- Intel (Nasdaq: INTC), Pfizer (NYSE: PFE), and ExxonMobil (NYSE: XOM) among them.

What's holding them back? In a word: Europe.

If you exclude the financial stress in Europe, a lot of good things are happening in today's economy. Jobs are bouncing back, exports are rising, profits are humming, and growth is steady. The problem is that potential fallout from a European financial crisis is too big to ignore. No one knows what might happen, but it's conceivable that a run on Europe's banking system could spark chaos similar to what we saw after Lehman Brothers collapsed in 2008.

What's the answer? Wharton professor Jeremy Siegel offered some thoughts during our exclusive sit-down earlier this month, including why stock prices could soar if Europe's policymakers get their act together. Have a look: