The God of the Bible offers a profound reply to the question "Who are You?" He replies "I AM that I AM" as if He is not readily definable.
There are many characteristics of this God that spelled out in detail; His desire for truth and justice, His love for the widow and orphan, His hatred of evil and injustice, His power and glory, and His plan for this world. So even if His whole is blurry, there are aspects of His character and abilities that are spelled out in detail.
Is it enough for a metaphysical debate? I have no idea.