Full Idea
If time is passing, then relative to what? How could time pass with respect to itself? Further, if time passes, at what rate does it pass?
Gist of Idea
What is time's passage relative to, and how fast does it pass?
Source
Adrian Bardon (Brief History of the Philosophy of Time [2013], 4 'Pervasive')
Book Reference
Bardon,Adrian: 'Brief History of the Philosophy of Time' [OUP 2013], p.96
A Reaction
I remember some writer grasping the nettle, and saying that time passes at one second per second. Compare travelling at one metre per metre.