Absorb What Is Useful (Push-Pull)
The quote, "Absorb what is useful, discard what is useless, and add what is essentially your own," which many claim birthed the idea of mixed martial arts, is not from Bruce Lee but Mao Zedong. (Lee was a notorious plagiarizer. But he did troll anticommunist racist chuds to unwittingly quote Mao.)
Mao surprisingly comes up often as recommended reading for martial arts, not just by self-identifying socialists but also by many Black and Brown martial arts elders.
Since Bruce Lee's primary thesis came from Mao, does that make Mao the real father of MMA? Hard to say, but he was definitely an unheralded contributor.
The premise of studying something old, keeping what is useful, discarding what is useless, and adding something new is an idea that's repeated throughout Mao's writings. Why? Dialectical materialism. Thesis + antithesis = synthesis. Mao applied dialectical materialism to learning, and Lee applied Mao's concept of learning to martial arts. Marx to Mao to Bruce Lee. (I should also add, Mao was a fan of Bruce Lee. Perhaps the feeling was mutual?)