Thank you all.
"We can't get outside the system or identify some independent variable, all we can do is accept some propositions as axiomatic or definitional, the rest is dependent on everything else and the aceptance of those axioms & definitions"
In a way, this is "Universal Solipsism". Existence is functional becasue it IS. This leads to the basic assumption (truism?) that the term "reality" labels a concept which is valid.
This assumption is basic to science, philosophy, relogion and our motivation to get out of (or stay in) bed in the morning. No components of the Universe are observable from outside the universe, since no "outside" can be shown to exist.
I do. however feel compelled to drop the word "objective".
Logic is a great servant but a lousy master. I use it as a structural framework only, fully realizing is limitations.
I discount Descarte. He is clearly a solipsist. Besides, practitioners of "lucid dreaming" are quite capable of asking such question while in the dream state.