大東流的第一性原理：從力學重新理解合氣
｜ First Principles

就像重力跟呼吸一樣，都是已經使用了才認知到，第一性原理（or ab initio method）也是用很久才知道原來有這個名詞，既有知識的線性推理不可或缺，但第一性原理的重新打底也是必要過程，線性推理在肌肉力學、物理學給予思考框架，第一性原理可以打破框架。

在我們系統中，柔術會學習關節控制(τ=F×d)、打擊(F=MA)、動量(P=MV)的使用，而合氣柔術則思考摩擦力(fs :fs ≤ μs * N, fk: fk = μk * N)，張力，質量(F=mg)，當然，就像開頭所說，這些都是用了才會知道，平常上課時候是不會討論到任何物理學公式的。

重要的是，合氣柔術需要從頭開始認知自己，也就是剛剛說的第一性原理，例如，最開始學的就是步法跟手解，從學習如何走路中重新理解自己身體質量與重心擺放，從跟對手的接觸學習面對抗力及摩擦力，拆解動作到最基本的結構，建構自己的認知，所有的學習都是累積在身體記憶中，不只是用腦還得用身體去記憶（是的，本文幫助不太，只能提供幾個思考的方向）。

初學者對於這套系統，往往直覺反應是「想要找到答案」，但大東流是一個系統，答案不會是僅僅一個公式，更何況，身體的記憶也需要由身體去認知，答案不是從語言或圖像可以獲得，必須讓身體學習跟感受，回過頭看，答案一直都在眼前，步法跟手解已經揭示很多答案，就像重力一直存在你也一直在呼吸一樣，重力跟呼吸每天都在用，但不見得人人都用的好。

不管是誰，入門後的學習路線都是這樣的：
LV1 不知道自己不知道
LV2 知道自己不知道
LV3 知道自己知道
LV4 忘掉知道的歷程而變成自己一部份

在LV2-3之間會是非常漫長的探索過程，但如果好好筆記所學的心得、想法，不斷檢視自身動作，在LV2-3所繞過的遠路都會是累積通往正確的道路。

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Just like gravity and breathing, you only become aware of them after you’ve already been using them. The same goes for the first principles (or ab initio method)—I used them for a long time before realizing there was even a term for it. Linear reasoning based on existing knowledge is indispensable, but rebuilding from first principles is also a necessary process. Linear reasoning provides a framework for thinking in muscle mechanics and physics, while first principles can break those frameworks.

In our system, JuJutsu involves learning about joint control (τ = F × d), striking (F = MA), and the use of momentum (P = MV). Aikijujutsu, on the other hand, considers friction (fs: fs ≤ μs × N, fk: fk = μk × N), tension, and mass (F = mg). Of course, as mentioned at the beginning, you only realize these after practicing them; during regular classes, we don’t actually discuss any physics formulas.

What’s important is that Aikijujutsu requires you to re-examine yourself from scratch—that is, to apply the first principles we just mentioned. For example, the very first things you learn are footwork and hand escapes. Through learning how to walk, you rediscover your own body mass and center of gravity. By making contact with your opponent, you learn about opposing forces and friction. You break down movements to their most basic structure and build your own understanding. All learning is accumulated in your muscle memory—it’s not just about using your brain, but also about letting your body remember (yes, this article doesn’t help much, it can only provide a few directions for thought).

For beginners, the instinctive reaction to this system is often “I want to find the answer.” But Daito-ryu is a system—the answer is not just a single formula. What’s more, your body’s memory must be recognized by your body itself. The answer cannot be obtained through language or images; your body must learn and feel it. Looking back, the answer has always been right in front of you—footwork and hand escapes have already revealed many answers. Just like gravity has always existed and you’ve always been breathing, you use gravity and breathing every day, but not everyone uses them well.

No matter who you are, the learning path after entry is always like this:
LV1: Not knowing what you don’t know 
LV2: Knowing what you don’t know 
LV3: Knowing what you know 
LV4: Forgetting the process of knowing and making it a part of yourself  

The journey between LV2 and LV3 can be a very long process of exploration. However, if you take good notes on your insights and thoughts, and constantly review your own movements, all the detours you take between LV2 and LV3 will accumulate and eventually lead you down the right path.