As Lewis Mumford and others have pointed out, the invention of the clock wrought the greatest change in human perspective of which we have record. It led to organizing reality according to its reference to an artificial sort of grid, one divided into unique and completely equal segments, and this in turn led to a way of viewing reality as consisting of things – events and people alike – as things that once were not, and then were for a countable quantity of these segments, and then were not again for all subsequent segments.
This is so irresistible a principle of organization that we can’t even imagine another, and yet it was not always so. Before the clock, the human significance of things – events and people – organized our reality rather than placement on an artificial grid. Thus for example the lives of our grandparents – though they be in the grave – could still be part of our own reality, not metaphorically but literally.
I suspect that heaven’s principle for organizing reality is much more like this older way than the mechanistic modern way. The reason why theological phrases like “heaven/God is timeless” or ‘heaven/God/the atonement exists outside of time” seem to us so empty of imaginative meaning, stating facts we cannot actually comprehend, however blithely we mouth them, is that we are creatures of clock-time. For us, time simply is the grid. Christ’s atoning act “took (past tense) place” in a certain “number” of segments on the grid, and does not even exist in “subsequent” segments of the grid (except in memory, causal aftereffects, etc, all of which occupy their own segments of the same grid).
In both Matthew and Mark, after guaranteeing His disciples recompense for the privations they are currently experiencing in following Him, Jesus qualifies what he has just said by adding: “But many that are first will be last, and the last first.” I believe He is here speaking of heaven-time – reality organized by significance – rather than clock-time, and what He is saying is that the order of significance there will be very surprising to those who have not begun preparing for it here-and-now.
And this, as far as I can see, is what underlies the meaning of many other gnomic Biblical claims such as “Jesus Christ is the same yesterday, today and forever,” “He was in the beginning with God,” “For he chose us in him before the creation of the world to be holy and blameless in his sight,” as well as many other things Christ Himself said.
In heaven’s true reality, there ‘was’ never, nor ‘is’ there now, nor could there ‘ever be’, a ‘time’ in which Christ’s atonement was not of infinite significance, is not there in its entirety.