What am I?

Am I something  
or nothing?  
A state of Being,  
or just recognised  
for my effect on other things?  
   
Theoretically, I exist -  
you know that I do.  
OK?  
Scientifically, I remain  
tantalisingly  
out of reach.  
You can speculate  
about how matter behaves  
but you're just  
not quite there.  
   
Mathematically,  
have you factored in  
my multiple factors  
(both positive and negative) -  
accurate to a certain degree,  
at least,  
in more ways than one.  
   
Musically,  
John Cage came close  
with his infamous 'piano' work, 4'33";  
both in its title  
and the contents of its score.  
   
Philosophically,  
does it matter anyway;  
how matter behaves, I mean.  
While we're on the subject,  
does anything actually  
matter at all?  
   
What am I? (8, 4)