Hi Willow,
I didn't read Uchiyama Roshi's writing as being about an absolute truth. I took to be more like Aristotle's accident/essence distinction (
https://en.wikipedia.org/wiki/Accident_(philosophy)) in the context of a larger context. So the particulars of our life are accidental/contingent but the four seals point to undeniable/necessary parts of our lives. They are kind of absolutes but not in an unmoved mover or first principle kind of way. Its more like when one take a close look at our world, our lives, the lives of others most people can see these properties (3 marks of existence/ 3 seals.) They appear to be enduring properties of living things.
As for big jiko. I just took that for Being being Being:) In all seriousness, the world is kind of a busy place with lots of comings and goings as well periods and places of quite and stillness. They are all part of larger happening that is the cosmos. Either way, I think these ideas are there to help guide (inform) our lives rather than be a kind of revelation of the truth. So they are more the support for a creeping vine rather than the answer to a question.
At least those are the mental secretions I've had when thinking about and reading some of the posts. What do you think?
Gassho
Sat today
Adam