security analysis

these have been testing times for many of us invested in the stock market one way or the other and so this has become an opportunity for me to reflect on my own investing strategy/idiosyncrasy. Lately I have been skimming through works of Ben Graham and Philip Fisher on the behest of a friend of mine, who I respect for his investing acumen and also for sharing his valuable investment ideas with me. I don't think I am any better at understanding intrinsic value or margin of safety than I understood them before but then the way the market has behaved in the last week or so its really hard to find anything that meets the conditions to pass Ben's quantitative analysis. It kind of makes you humble when you look at your portfolio and wonder how much does one really knows about the underlying securities, if nothing else I can at least make out the difference between an investment and a speculation, but then as Descartes reminds us 'It is not enough to have a good mind. The main thing is to use it well.'