What is the Most Important thing? For the last twenty years I’ve been writing occasional memos to my clients—first at Trust Company of the West and then at Oaktree Capital Management, the company I cofounded in 1995. I use the memos to set forth my investment philosophy, explain the workings of finance and provide my take on recent events. What, exactly, is “the most important thing”? In July 2003, I wrote a memo with that title that pulled together the elements I felt were essential for investment success. Here’s how it began: “As I meet with clients and prospects, I repeatedly hear myself say, ‘The most important thing is X.’ And then ten minutes later it’s, ‘The most important thing is Y.’ And then Z, and so on.” All told, the memo ended up discussing eighteen “most important things.”