Robert Shiller, Yale professor, and founder of the S&P/Case-Shiller home price index just appeared on CNBC to talk about the latest Case-Shiller report, which showed home price growth slowed some in July. Shiller also talked about the stock market. Author of the investing classic 'Irrational Exuberance,' Shiller gave a great insight into the current psychology of the stock market rise, and an alternative theory about why the market keeps going up.