"What is that?" the Doctor asked, perplexed.
"A concept," Lincoln explained for him.
The electronic spirit world, Digital Heaven, Cyber Underworld—they were all different facets of the same concept.
And these three facets shared one common feature:
They were closely related to [death].
This was also the impression that Lincoln hoped to pass on to all users in the future:
[Digital Life] was not about extending life eternally, but about starting a second chapter of life.
Only those who had lived their first chapter of life and were approaching the end of their lifespan could be transformed into digital lives, and at the same time, they would have to give up most rights from before the transformation.
Of course, in Lincoln's plan, the conditions for transformation were not difficult to meet—as long as one was not a major villain, even a perfectly ordinary life would suffice to meet the criteria.