It’s interesting to note that in Jewish terminology, existence is phrased in terms of the thing-as-experienced, not the thing-in-itself, as it would be objectively known if it were possible. For example, the Rambam opens the Yad by telling you that there is a First Matzui, and He is mamtzi everthing that is nimtza. The word “nimtza”, which is used to mean existence, is from the root /m-tz-a/, to find. Experience.
When something is real enough to have impact, we say is has “mamashus”. Or we say that something is mamash exciting, where in English it would be “really and literally exciting”. The word itself, though, literally means “tangibility”.
Perhaps this is because halakhah exists to change the person following it. “The person is made [nif’al] according to his actions [pe’ulaso]”, as the Chinukh often says. Thus, the reality that the halachacist must address isn’t the objective abstract existence, rather, it’s the one experienced and shapes the person.