每日原則：不必過於精確

理解“差不多”這一概念，使用粗略估計法。因為我們的教育系統過於重視精確，所以擅長粗略估計這個技能的價值常被低估。這會影響概念化思考。

例如，當被要求計算“38×12”時，大多數人是以緩慢費力的方式計算，而不是簡單地把38四捨五入成40，把12四捨五入成10，然後快速地確定答案在400左右。看看冰激凌店的例子，想一想，與其費力地把所有關係弄清楚，快速看到各個點之間的大致關係，是多麼有用。費力進行精確計算是愚蠢的，但大多數人就是這麼做的。

為了做出有效決策，你需要在“差不多”這個層面上理解大多數事物。當每次有人做一個宏觀的“差不多”的陳述，而有些人反駁說“並不總是這樣”時，我的本能反應是，我們也許要丟西瓜撿芝麻了，即討論例外而不是常規，而這將讓我們看不到常規。為了幫助橋水的員工避免這種浪費時間的情況，我們的一位剛從大學畢業的投研人員說了一句我經常複述的話：“當你問一個東西對不對而對方告訴你並不完全對時，那它應該大致是對的。”

Understand the concept of “by-and-large” and use approximations. Because our educational system is hung up on precision, the art of being good at approximations is insufficiently valued. This impedes conceptual thinking.

For example, when asked to multiply 38 by 12, most people do it the slow and hard way rather than simply rounding 38 up to 40, rounding 12 down to 10, and quickly determining that the answer is about 400. Look at the ice cream shop example and imagine the value of quickly seeing the approximate relationships between the dots versus taking the time to see all the edges precisely. It would be silly to spend time doing that, yet that’s exactly what most people do.

“By-and-large” is the level that you need to understand most things in order to make effective decisions. Whenever a big-picture “by-and-large” statement is made and someone replies “Not always,” my instinctual reaction is that we are probably about to dive into the weeds—i.e., into a discussion of the exceptions rather than the rule, and in the process we will lose sight of the rule. To help people at Bridgewater avoid this time waster, one of our just-out-of-college associates coined a saying I often repeat: “When you ask someone whether something is true and they tell you that it’s not totally true, it’s probably by-and-large true.”