Excerpt from <span class="chinese-post-title">拳意述真自序</span> the Author's Preface in <span class="chinese-post-title">拳意述真</span> Boxing Concepts Explained Authentically

一則

三派拳術。形式不同。其理則同。用法不一。其制人之中心。而取勝於人者則一也。按一派拳術之中。諸位先生之言論形式。亦有不同者。蓋其運用。或有異耳。三派拳術之道。始於一理。中分為三派。末復合為一理。其一理者。三派亦各有所得也。形意拳之誠一也。八卦拳之萬法歸一也。太極拳之抱元守一也。古人云。天得一以清。地得一以寧。人得一以靈。得其一而萬事畢也。三派之理。皆是以虛無而始。以虛無而終。所以三派諸位先生所練拳術之道。能與釋儒道三家。誠中。虛中。空中之妙理。合而為一者也。

孫祿堂

" The postures of the three boxing arts are different, but their theory is the same. Their applications may be different, yet they have controlling the opponent as their core, and so they defeat opponents in the same way. Within a single system of boxing, everyone’s explanations and postures are not identical, owing either to how they use them or just to differences from one person to another.
The methods of these three boxing systems begin with the principle of oneness, divide from there into the three distinct branches, then end up united again in the principle of oneness. Each of the three systems has its own way of oneness: Xingyi Boxing’s sincerity is a pure oneness, Bagua Boxing’s infinity of techniques is a returning to oneness, and Taiji Boxing’s embracing of original nature is a maintaining of oneness. It was said by men long ago [Laozi – Daodejing, chapter 39 / Zhuangzi, chapter 12]: “The sky obtains oneness by being clear. The ground obtains oneness by being firm. Man obtains oneness by being smart.” / “Obtaining the One, all things are accomplished.” The principle of the three systems is always to begin in emptiness and to end in emptiness. Therefore the way the teachers of the three boxing arts practiced can be equivalent to the three schools of Confucianism, Daoism, and Buddhism – with their special theories of sincerity, undifferentiation, and non-identity – merging to become one."

Excerpt from the translation by Paul Brennan, to be found in the Brennan Translation blog.