Back in my post on the Nature of Wrath, Rey made the following comment
...my problem doesn't have anything to do with the propitiation but with the "united with Him on the Cross through the Holy Spirit" bit when 1 John 2:2 says that Christ was a propitiation for our sins and the sins of the world. If we're united in the Holy Spirit to Christ on the Cross then it sounds like the world is united in the Holy Spirit to Christ on the Cross...and they can't even receive the Holy Spirit (John 14:7). I don't know, it just really sounds like there is a line being fuzzed out in there when the connection to Christ on the cross is the Holy Spirit.
I promised a response, so here it is. Unfortunately, I'm going to answer in a bit of a roundabout way...
In the circles that I seem to run, there is a mini-obsession with limited/unlimited atonement. Every model of the atonement that is studied gets heavily analyzed on that particular aspect of the model. To keep things interesting, I keep pointing out that universalism is another possibility, and the discussions really get going.
Though the discussions are certainly interesting, the downside is that much more important issues regarding the atonement are overshadowed by the "extent of the atonement" discussions. Issues of Christology, anthropology, sin, death, and the subjective/objective nature of the atonement all have greater impact and are of far more importance than the limited/unlimited issue.
As such, when I am discussing my model of the Atonement, I doggedly remain silent on this issue. I want people who are thinking about this model to be thinking about the more important issues rather than get sucked into a minor point. That is to say, I'd hate for a person to reject the whole model just because they disagree with my stance on limited/unlimited/universal atonement.
That being said, most people seem to think that my model demands the limited atonement view. I disagree. I think my model is flexible and robust enough to support limited, unlimited, and universal atonement:
1) Limited atonement. This one is fairly straightforward. The elect are united with Christ on the cross via the Holy Spirit. The non-elect are not. Christ dies only for the sins of the elect.
2) Universal atonement. This one is, if anything, even more straightforward. All are elect, and therefore, all are united with Christ on the Cross via the Holy Spirit.
3) Unlimited atonement. This one take a little work, but not much. The elect are united with Christ on the cross via the Holy Spirit. This union is a marital union (Eph 5) and the Spirit indwells the elect. However, it is also clear that Christ is united with all humanity in some way, though not in a marital union (Matt 25:31ff). Let us suppose for the sake of argument that this union is achieve via the Holy Spirit as well, but not through indwelling, as with the elect, but in some more temporary manner, just as the Holy Spirit would be with some in the OT but then depart. Thus it is conceivable that all of humanity is united with Christ on the cross, though not necessarily in a marital union. For those where the Spirit's presence is temporary, the union stops with the cross and does not include the resurrection. Thus they are punished for their sins in Christ, but are left dead. They are stranded in Hell without union with Christ and His resurrection to bring them out. In this scenario, Christ really does die for the sins of the entire world, but the benefits of the resurrection only apply to those who are maritally united with Him. As I've (tried to) note before, the crucifixion is an incomplete act. Without the resurrection, it is worthless (1 Cor 15:17).
As you can see, the unlimited atonement scenario requires quite a bit more nuance than the others, but that is pretty much true for all unlimited atonement scenarios.
At any rate, hopefully I've shown that my model of the Atonement does not require any particular view on the limited/unlimited/universal atonement issue. Any by so doing, hopefully I've answered Rey's worries as well.