Very often physicists with reputation never ask
uncomfortable question, which they dont like.

As is, what property of space, time or matter
makes the universe three dimensionally?

It must be the matter, because time and space
are rather mental construction, I mean, this can
be proved, that these are, and only are, mental
construction. Moreover, matter is considered as
being energy in many groups. Energy again, is
not well posed. What is going on here? Why are
they telling us that we live in three dimensions?

Are we sure we live in a three dimensional manifold,
where 3D relativity holds good in its domain of
applicability? What proofs do we have in hand?