I do appreciate thoughtful Replies such as yours always are, Mr. Ruis. I would say "material existence" conveys an understanding that there are people who believe that an "immaterial" 'reality' does exist.

Whether it exists or not--as well as what it might be like--are all matters of strictly personal knowledge: knowledge that is absolutely true, but only for the individual. Knowledge of material existence has a means of commonalty, of being shared by virtue of a reflexively shared (or at least sharable) experience (i.e., people can know what the other experienced by virtue of what they experienced for themselves, without anyone having to take anyone's word for anything), that no version of any immaterial existence can possibly have.