While many analysts have turned bearish on stocks in recent months, Thomas Lee, founder of Fundstrat Global Advisors, has maintained a bullish tune.

And Greece's debt crisis, which he calls a "sideshow," hasn't changed his mind. "Greece isn't the systemic risk that it was three years ago," he told CNBC. "Focus on U.S. fundamentals, which have been really good."

While the economy shrank 0.7 percent in the first quarter, the Atlanta Federal Reserve's forecasting model indicates 1.9 percent growth for this quarter.

"I know people are fearful about rising rates and Fed tightening and what it means," Lee said. "But at the end of the day, we're actually seeing reflation — the good kind of rising prices in the U.S. I think it's bullish for capital spending and bullish for housing."

Consumer prices rose 0.4 percent last month, though they were unchanged for the 12 months through May. The Fed has indicated that it's likely to boost interest rates later this year.

Star mutual fund manager John Hussman, president of Hussman Investment Trust, doesn't share Lee's enthusiasm. Don't be fooled by the fact that the S&P 500 index is hovering within 1 percent of its record high, he says.

"The financial markets are establishing an extreme that we expect investors will remember for the remainder of history, joining other memorable peers that include 1906, 1929, 1937, 1966, 1972, 2000 and 2007," Hussman writes in his weekly commentary.

"The failure to recognize this moment as historic is largely because investors have been urged to believe things that aren’t true, have never been true, and can be demonstrated to be untrue across a century of history."

So what are the un-truths? The principal one is that the Federal Reserve is boosting financial asset prices, Hussman says.

"In fact the primary driver of financial markets in recent years has been pure speculative risk-seeking. While risk-seeking is encouraged by monetary easing, it is not a reliable outcome."

The Fed has kept its federal funds rate target at a record low for 6 ½ years, and its balance sheet has ballooned to $4.5 trillion.

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