Jeff Sommer talks to Harvey Markovitz, considered the founder of portfolio theory, on share prices and the stock market. Markovitz says portfolio selection are the two most important words he wrote and the ones to remember. Building a diversified portfolio is the most important thing in investing. Markovitz says investors should forget about individual stocks and their oscillations, and buy low cost index stock and bond funds. Allocating these in a way that depends on the volatility and risk that the particular investor feels comfortable with. Rebalance the portfolio as needed periodically, and change allocations. Other than that do other hobbies, things that give you a greater sense of reward. Markovitz was deeply influenced by Hume's ideas of skepticism and the thought that one was never sure about the probability of an event occuring even if it had ocurred before.