But, what exactly is an investment philosophy and how is it different from an investment strategy? According to Damodaran, an investment philosophy “is a core set of beliefs about markets, a behavioural set of assumptions about how markets work, how they fail to work, and how to take advantage of common mistakes made by investors in the markets. This is as opposed to an investment strategy, such as buying low price to earnings stocks or going contrarian.” And why does one need an investment philosophy? Because without it, your portfolio is going to swing from one strategy to another, based on what worked best recently, leading to a huge turnover ratio, large transaction costs and poor returns.