1. In the beginning ...

1.1  Time is a mystery, pure and simple. There is no way to get one's head around it.

1.2  I can get my head around the future: I can conceive of time going on forever. But I cannot get my head around the past. There are two options, and neither one makes intuitive sense:

• Option 1: Time had a beginning, and therefore "before" the beginning there was nothing, not even a "before." But how can this be? How can there be "nothing," not even time itself, and "then," something, a universe with a beginning and a history?
  

• Option 2: Time has no beginning -- rather, it has been going on "forever." But how can this be? Things have been happening -- forever? Past time is infinite? That's a mystery.
  

1.3  When I was a boy of perhaps ten years or so, these matters troubled me. So I explained the dilemma to my mother and asked her for the answer. She said, "Maybe time is not like a line, but more like a circle." And she took a pencil and drew a circle on a piece of paper. I contemplated time as a circle, and new questions arose: Well, what happens when you go all the way around the circle? How long does that take? And then does everything start repeating itself over again? And just how and when did this "circle of time" come into being, anyway? And so on. My mother's diagram did not help, because our actual day-to-day experience of time is not like a circle, it's like a line or arrow.

1.4  So, time is a mystery. It makes sense only "locally": for the past we can remember or reconstruct, the present we live in, and the future we can to some extent forecast. At time spans greater than "local" -- potentially infinite past, potentially infinite future -- our little causal reasoning dissolves into mystery.