Benjamin Graham
Benjamin Graham's classic case for intelligent investing centers on a few durable ideas: distinguish investment from speculation, treat market swings as opportunity rather than instruction, and insist on a margin of safety before you buy.
Protecting capital starts with buying securities at a meaningful discount to their estimated intrinsic value.
The stock market is best treated as an emotional business partner whose changing quotes can create opportunity but do not determine underlying value.
A simple valuation formula can provide a baseline estimate for a company's value, but it should be used conservatively rather than as a precise answer.