MY INTERLOCUTOR: "Where my main disagreement lies is with your statement that 'all that really exists or has duration is the present.' For, if only the present exists, then time does not exist. For this is the very definition of atemporality: being without succession in a constant undivided NOW. To be sure, neither the past nor the future have a duration greater than (or less than) zero in the present. But, neither does the present have a duration greater than (or less than zero) in the present. For, however long the duration is of the present, for that same length of time, time stands still. And when time stands still, time does not exist, for no temporal succession
occurs during that 'time'. So, in order for time to exist, the length of the duration of the present cannot be anything other than zero."
EDGAR: One could argue that a tense like "present" implies duration since we could and often do view "the present" as a temporal distinction. The argument set forth above only works if one accepts your definition of "atemporality." As one who believes in an A-series of time, I do not define "atemporality" as "being without succession in a constant undivided now." My view is that the present (i.e., now) necessarily shares in temporality insofar as it involves temporal succession. Richard Gale takes up this subject in a work entitled "Has the Present any Duration?," Noûs, Vol. 5, No. 1. (Feb., 1971): 39-47. He argues that certain problems arise when we talk about "the present" since it is possible to equivocate when employing this language. Gale makes a distinction between the durational present and the punctal present. An example of the former distinction is when we speak of the current year (2008) as the present; conversely, we can refer to the present or "now" in the sense of a particular moment of the current year (i.e., 4:15 on April 4, 2008). Unless we make a clear distinction between which "present" we're talking about, antinomies might result.
INTERLOCUTOR: "If the present is indivisible, how can it have a duration other than zero? For no number other than zero is indivisible."
EDGAR: The present is not necessarily indivisible. Besides, it depends on which "present" you have in mind. But even the present (in terms of this day, April 4) appears to have finite temporal parts or some type of extension. There is an informative article by C. W. K. Mundle "Augustine's Pervasive Error concerning Time," Philosophy, Vol. 41, No. 156. (Apr., 1966): 165-168. Mundle critiques the Augustinian assertion that "No one would deny that the present has no duration" (Confessions 11.28). Using some of his examples, I might ask, if the present has no genuine duration, then how is it possible for me to hear a series of sounds now that I recognize as my favorite song? Or what if I am now having the experience of visually perceiving my 2005 BMW? How can I make sense of this (current) visual perception in terms of a durationless present?
"Thus, I argue that the past, the present, and the future have an atemporal mode of existence in the present. And by an atemporal mode of existence, I mean a non-durational mode of existence. If you reject this concept, then how can it be consistent with your views for you to speak of the past as 'being' potentially infinite, or to say that the past 'is' potentially infinite? Wouldn't consistency require you to say that 'the past was potentially infinite', with the implication being that the past is now no longer potentially infinite?"
Firstly, I do not buy into the notion of tenseless time. Maybe it is not your intent, but it seems that you have verbally abolished tense vis-a-vis time and you're now content to have a tenseless past, present and future "in the present," which still does not make sense to me unless what you're trying to affirm is a B-series of time in A-series language. If I speak of the past as "being" potentially infinite, I do not mean that the past is still in existence. I have made it clear that I affirm the A-series of time which claims that the past is no longer and the future is not yet. When I used the language you allude to above, I did not mean to imply that I believe God's potentially infinite past still exists. I was simply trying to predicate potential infinity of the past: it is only a suggestion that is being made here.
"I am curious as to where John of Damascus speaks of time as having existed in an unmeasurable state prior to the coming into being of the created order. Wouldn't 'unmeasurable' time have to be indivisible, and thus atemporal?"
I came across the references in Stephen T. Davis' Logic and the Nature of God. He culled the remarks of John of Damascus from a book written by Nelson Pike (God and Timelessness), which I have read and subsequently documented the references to John of Damascus for myself. You can find the Damascene's observations on time in An Exact Exposition of the Orthodox Faith. His words appear on p. 181 of Nelson Pike's work. Keep in mind that Davis and Pike interpret John of Damascus as making the claim that God once existed in unmeasurable time or that unmeasurable time is somehow tied to God's nature.