Could the Members of the Trinity have Switched Places? (QoW #1012)

If the Son is not eternally begotten of the Father, is it arbitrary which person of the Trinity is called "Father" and which is called "Son"? And what distinguishes the three persons from one another in the first place? Dr. Craig responds to a reader's two worries about his view of the Trinity, drawing on the distinction between the economic and the ontological Trinity and on the observations of Marcellus of Ancyra, one of the orthodox leaders at Nicea.