The original note, as written at the time
A group of humans find out that the path to immortality requires unselfish service. However, one cannot always know whether they are in the good book or not, but there is always evidence of people with immortal paths.
Ongoing development
It was discovered by accident, in the sense that every true thing about immortality is discovered by accident and then claimed as a policy.
The path is unselfish service. Not sacrifice — service, sustained, unglamorous, and unrecorded, because the moment it is recorded it becomes a transaction and a transaction is not service. This is not my interpretation. It is what the pattern shows, and the pattern is old enough to be read.
The difficulty is that you cannot know where you stand. That is the entire structure of the thing, and it is why it has never produced a caste of saints. You may serve for forty years and be nowhere. You may be a careless man who did one thing in a market, without thinking, and be on the path.
But there is always evidence. Not proof — evidence. In every generation a few people do not age. They are noticed, and then they are explained, and then they are visited by people who want to know what they did, and they give answers the visitors do not want. Nothing dramatic. They say: I did what was in front of me. They say: I did not keep a record of it, which is why I cannot tell you.
So a quiet industry has grown around them. Men travel for years to sit with a person who has not aged and ask what the secret is, and the person says something ordinary, and the man goes home disappointed and writes a book about it. The books all contradict each other, because each one is a translation of an answer by someone who was not a saint and wanted to be.
The genuinely old ones are careful about this. I have met two, and neither would accept anything from me, not even a meal, and both of them explained it in the same way: that the moment you accept a reward for the path you are no longer on it, and that this is not a rule imposed by anyone but simply the way the thing is.
What nobody has worked out is what the ledger does with a person who did enormous good and enjoyed it. Because we all enjoy it. That is the awkwardness at the centre of the whole business. If the thing requires that you not know you are doing it, then the self-aware philanthropist and the man who never thought about it are in entirely different places, and only one of them can buy a building with his name on it.