Ostriches do not actually bury their heads in sand and pretend that nobody can see them.Metaphorically speaking, vast numbers of humans today do precisely that.
The point is that they pretend that if they don't look behind them, God won't realise that they are there.
This is the bosom buddy of "If I have the opinion that God does not exist - then He probably doesn't."
It takes real ability to live a life which is quite that devoid of all logic - not to mention common sense.
