Celestial Great Saints were creatures born with infinite lifespans—well, probably.
After all, who the hell knew what mystical factor had made the first batch of stars skip the steps they ought to have gone through—awakening, cultivation, exploration, development—and directly become omniscient, omnipotent spirits capable of pinning causality to the ground and [beep]ing it? No, correction: not even ghosts knew. Not even ghost immortals could possibly know.
Wish Fulfillment could only speculate that they were, by logic, naturally endowed with eternal life.
Perhaps precisely because of this, in the Celestial Great Saints' view, all creatures with finite lifespans were inherently afflicted with "design flaws." The Nascent Soul Method was what they provided to the myriad living beings, allowing them to avoid their inborn defects.
And for those short-lived species without natural eternal life, how to transform their minds was also extremely important.
This was not idealism or voluntarism. The structure of the flesh determined the state of the mind, but the mind could likewise act in turn upon the flesh.
Adjusting one's mind to the state of an Immortal was also in keeping with the Nascent Soul Method's original design. A settled mind meant a stable cultivation body.
In truth, the natural "will" of most short-lived species could not adapt to immortality.
Put it this way: "evolution" only needed to ensure that an individual survived to reproductive age and passed on the spiritual resonance of its bloodline. The constant negative state called "decline," acquired after an individual passed reproductive age, was something "evolution" could not overcome.
And as the control system of the flesh, the "mind" had no need to prepare itself for eternal use.
Ordinary civilizations would gradually overcome this problem through cultivation known as "mind-holding."
But the Ming Clan would not. They had never prepared for "eternity" at all.