The question is misleading. Bitcoin doesn't have backing. But other things may be backed by bitcoin.
Exactly. My favorite answer is: The same thing gold is backed by.
Not exactly.
Bitcoin and gold are both backed by the same thing - their unparalleled utility as a medium of exchange satisfying Aristotle's prerequisites:
So you tell me "not exactly" and then you repeat my words? Huh?
Yes, but no. You were half right.

'Not exactly' referred to your assertion that "Bitcoin doesn't have backing." Bitcoin and gold are backed by their utility as ideal media of exchange.
Oh I see, the problem is actually that you don't understand what the meaning of "being backed by" is.. Tell me, can I cash in my 1btc or 1gram of gold and get utility as ideal medium of exchange out of them? And how does utility as ideal medium of exchange look like?
valued properties != backing, mkay?