[Advaita-l] Ishwara Turiya?

[Bhaskar YR]

I am interested in what primary sources say because I would like to
understand, with textual evidence, what Sankara says.

praNAms
Hare Krishna

shankara clearly says in sUtra bhAshya (for example araMbhaNAdhikaraNa) 
that Ishwara's existence, his omnipotence, omnipresence etc. holds good 
only in vyAvahArika.  However, at somany places shankara uses Ishwara & 
nirupAdhika brahman interchangeably !!

Hari Hari Hari Bol!!
bhaskar