The dullest ink is better than the best memory — what is the principle behind this?

Memory, meaning rote memorization when one does not understand, is a function of the mind consciousness. What has been memorized has not yet been perfused into the manas, so the manas does not yet understand it. How can one effectively perfuse the manas so that the manas comprehends and can recall it anytime and anywhere in the future? That requires constant writing. Writing is actual practice; writing is very slow, and while writing, one is simultaneously perfusing the manas. In this way, the manas can easily come to understand.

Writing slowly is itself meditation (samādhi), enabling concentration, so the manas can digest and absorb the content. Later, when encountering this content, one will understand it without needing to deliberately memorize it. Content memorized by rote without understanding is easily forgotten and unreliable, and even less can it be recalled in future lives. When the manas comprehends, one can also receive its benefit in future lives.

Rote memorization means that the manas has not understood the material being studied, and everything relies on the mind consciousness's forced memorization and recitation. No matter how fluently the mind consciousness recites, the manas still does not understand. But when the manas and the mind consciousness genuinely understand the material being studied, there is no need to memorize or remember it at all; when it is needed, it can naturally be brought forth and applied with ease. People with poor comprehension like to memorize; people with good wisdom, once they have understood, let it go.

The difference between the mind consciousness's cultivation and the manas's cultivation is enormous. The wisdom of the manas is true wisdom; the wisdom of the mind consciousness is false wisdom.