Mr. Buffett, who is 84 years old, has never wavered in the principles he learned from his mentor, Benjamin Graham: Stocks are ownership stakes in businesses, not pieces of paper or blips on an electronic ticker; their market prices often are driven by the mood swings of investors rather than by the value of the underlying businesses; and investing is worthwhile only when value exceeds price by an amount great enough to create a “margin of safety.”
Nor has he ever changed his views on three of the most powerful weapons in the investing arsenal: cash, emotion and information.
Source: What You Should — and Shouldn’t — Learn from Warren Buffett – MoneyBeat – WSJ