Never before in recent  history have the prospects for investors appeared so dismal. This statement may seem absurd. After all, economies around the world appear more stable than ever. Stock markets aren’t so evidently buoyed by irrational exuberance as they were in the late 1990s. Furthermore, the alternative-assets revolution has greatly expanded the range of potential investments. But that’s no comfort when just about every major asset class is perilously overvalued. In the investment world opportunities normally exist for those who are prepared to stray from the herd. After the 1929 stock market crash, Treasuries soared as the economy collapsed and a severe deflation set in. Investors had even more choices when the technology bubble burst at the beginning of this century. Enthusiasm for the New Economy had overshadowed compelling opportunities in commodities, small-cap and value stocks, real estate, emerging-markets equities and bonds, and so forth.  Today the situation is...