Tai Chi fighting basic knows Four Characters Secret
The postscript explains that to understand the Four Characters Secret, one must first understand the energy; without this understanding and reaching a highly refined level of practice, it's impossible to fully grasp it. This might sound mysterious, but practicing push hands involves a process of 'gradually understanding the energy from familiarity and progressing to a divine level of understanding.' Only after passing the initial stage can one gradually understand the "Four Characters Secret." Of course, due to individual differences in insight, even with the same effort, comprehension can vary in timing.