Let's take a few of the theories/observations we've been fiddling with and combine them.
First, the wonderful observation that things seem to happening twice.
Second, the arguments set forth in the big 'social construction of reality' scene.
Now, what they said in that scene (massive paraphrasing to follow) was that there are two opposing theories to the construction of reality. The first one being that reality is created internally, by the thoughts and decision of each individual. And the second, focusing on the externality of social phenomenon.
So lets say that the reason we are seeing everything twice is that we are seeing each major event through the lens of each of these theories. That the first time things happen, they are 'created' internally. As in, they are the result of the internal choices and actions of the people involved.
ex: The first time Willow 'loses' Tara, it's a result of her own actions and decisions in doing the 'forget' spells, and Tara making the choice to leave in response.
And that would mean that the second time it happens, the reality is externally created. Meaning it's something which is completely out of the control of those involved and only the result of outside forces acting upon them.
ex: The second time Will loses Tara, it's all about the accident and things which neither of them could possibly controlled.
The general idea would seem to be that what we've been seeing all season, the 'realities' of each of the individual characters were internally created. Their problems, their troubles, were all things which they themselves had controlled and been responsible for. This is another thing we've noticed, nearly every plotline has been the result of a their own actions.
But that the end of the season is about an externally created and controlled reality. In other words, the reality defined and controlled by the wish. And that what we see in that reality is each of the characters reliving what has happened to them only this time with the events surrounding them being a result of the wish and it's consequences. And this being the reason for the extreme, out of control nature of the events as they are repeated. Because the fact that they are 'out of control' is precisely the point.
Edited to add:
Being out of control/forced to do something against your will (another entendre for that ep title) has been another major theme as well - Will trying to control Tara's memory, Warren's 'cerebral dampener', basically the entire musical, Buffy trying to control her reality in NA, FutureXander controlling Xander's visions in HB, and people being forced to stay in the house because of Dawn's wish.
Ari
[This message has been edited by Ari (edited March 22, 2002).]