Augustine tells us that built into the human soul is a God-Shaped Hole. This is apparently the cause for all human longing and the drive for all activities. It is as though we are trying to fill this space but that we will never fill it because the only thing that can is the divine.
Lacan tells us that as soon as we enter into language, into the symbolic order, we are immediately left with a problem of what we have left behind. We want to return to it and will create all manner of substitutions that represent the thing left behind. However, we cannot describe it because we left it in order to enter the symbolic order.
Now, are they talking about the same thing? Not really. As far as Lacan is concerned, Augustine has entered into the symbolic order of Christianity and is attempting to use the language of that order to describe the thing he has left behind. In other words, when Augustine speaks of the God-shaped hole he is using only what he has available to describe it, but in the end, merely calling it the God-shaped hole is just a substitution for the thing he has left behind. The God-shaped hole, and the God that is used to fill it, are both merely fraudulent idols (objects with a false meaning) that we rely upon in order to help us cope with the separation from the thing.
So the thing that drives us, Augustine’s God-shaped hole, it not God-shaped and it is merely an attempt to find satisfaction of our desires. And this is not the Christian message.