I think this is really interesting. From a real-world philosophy it seems that this would be more in the tradition of a Buddhist monk than a medieval Christian monk. To me this sounds a lot like an elven lore-master, likely one of great age, looking to pass along knowledge before he sails to the West.
The deep truths you mention about the status, the nature, and the condition of Arda; its makeup and how living things fit into it, would be really only known by Elves. Specifically, this information would likely lie in the hands of Noldorin exiles or those who have been taught by them, or those who were around during the First Age. Imladris is the only place I can think of that would be a center of this kind of knowledge at this particular time. Galadriel and Celeborn would have this level of awareness also, of course; as would the Istari - perhaps this individual spent time living in proximity to Lorien or Imladris or one of the Istari?. This is deep stuff that your average run of the mill Elf or Man wouldn't really be aware of, except those who are deep in the lore of the Wise.
I guess it's possible that a lifelong scholar of Men steeped in the lore of Minas Tirith would know some of this - but late in the third age those types of individuals would be quite rare.
Just my opinion of course
Galadhloth, Hunter 100, Glirithil, Mini 100, Calanor, LM 100, plus lots and lots of alts
Watchers of Elendil ~ Landroval ~ Crickhollow ~ Tarciryan Knights
~~~~ Imladris in the Forgotten West ~~~~