How can something be present as well as absent?  Consider the observation of writer Robert Nozick that, "We don't need to choose between presence and absence."  Although it may difficult to know precisely what Nozick means (he has written extensively on nothing and nothingness), if we set it into the framework of our question, we come to some intriguing conclusions.
     Clearly, from any rational standpoint, we all experience presence.  We all experience being "here," we all experience exchange with other things that are "here" as well.  We may not be able to "prove" whether anything is here, for we would be using what we assume to prove what we also assume in turn.  But we know that we have some sort of experience of, as the philosopher Martin Heidegger put it, beingness.
     Yet with equal clarity, we can assert that we all experience absence.  We all experience a loss of presence, in some form, in the course of our lives.  Privation is intrinsic to existence.  But can we experience both presence and absence simultaneously?
     Think about memory.  We remember, as presence, yet we do not see such memory, as presence.  Physically, it is no longer with us.  But we sense its presence, absent yet present.  And we go on.
     Now think about faith.  If we believe in something, whatever it may be, we believe in its fact, its presence, now or future.  We believe in it even if it is now absent.
     In an old parable that recounts the tale of a person's journey--his life journey--with God, the author pictures a pilgrim walking along a long and lonely beach, land spreading out endlessly, oceans spilling into infinity, and wondering about whether God is with him, for he does not seem to really know.  He can't see him.
     At journey's end, after the passage of death, the pilgrim comes face to face with God, and asks God, "Where were you?"
     "Ah, my child," God replies, "I was with you all the time.  Did you not see my footsteps?"
     "No, Lord," the pilgrim answered.  "Where were they?"
     "In every moment of your life, child," God responds.  "You just didn't see them."