Lite Version: Summary of Core Points 1. The fundamental investment logic can be summarized in one sentence: buying stocks is buying companies, and the key is understanding the company's future cash flow—simple but extremely difficult, most companies are hard to understand. 2. The true definition of a margin of safety: it's not just the stock price being below net assets, but your depth of understanding of the company—being knowledgeable is the greatest safety cushion. 3.