The logic (and joy) of Calvinism - why substitution is so important

Several hundred years ago, Puritan theologian John Owen broke the back of his contemporary Arminians' logic of a general atonement by putting forth and defending the argument that Christ on the cross died for all the sins of a particular people (not just some abstract idea of all of "humanity"). And while this word "particular" arouses the most dreadful feelings of the supposed immorality of God in many professing Christians, when seen rightly, we can declare with C.S. Lewis that God's irresistible grace towards us in Christ's substitutionary sacrifice "plumbs the depth of the Divine mercy...[and that] the hardness of God is kinder than the softness of man, and His compulsion is our liberation." See the argument below:

The Father imposed His wrath due unto, and the Son underwent punishment for, either:

1. All the sins of all men;
2. All the sins of some men; or
3. Some of the sins of all men.

In which case it may be said:

1. That if the last be true, all men have some sins to answer for, and so, none are saved.
2. That if the second be true, then Christ, in their stead suffered for all the sins of all the elect in the whole world, and this is the truth.
3. But if the first be the case, why are not all men free from the punishment due unto their sins?

You answer, "Because of unbelief."

I ask, Is this unbelief a sin, or is it not? If it be, then Christ suffered the punishment due unto it, or He did not. If He did, why must that hinder them more than their other sins for which He died? If He did not, He did not die for all their sins!

Now Owen is referencing here the extent of Christ's substitutionary atonement - that is, for whom did Christ suffer and die when standing as the substitute to receive God's wrathful punishment on sin? Owen says that if Christ is actually saving and exonerating people from their sins, then he did it for a particular people...an elect people, as the Bible calls it. If he died for all men, then he must not have died for all their sins, because there are many who still face judgment for their sins. Greg Forster plays on this argument in his book The Joy of Calvinism:

The Calvinist will not say, "Jesus makes salvation available and then I avail myself of it," because he sees that this is really the same as saying Jesus doesn't save us; indeed, it is just a hair's breadth away from saying that we save ourselves. For once we make the effectiveness of the cross and the tomb subject to some subsequent process, we have emptied them of substitution, and with substitution all the substance of our salvation. And once we deny that Jesus determines the effectiveness of his own work, we make its effectiveness subject to our actions, thus attributing the outcome of salvation to ourselves (in effect if not in so many words).

Few would disagree with the statement that a true Christian is a person who clings for salvation, not to the church; not to the sacraments; not to the Bible; not even to the proclamation of the gospel or the believer's belief in it; but to the cross and the empty tomb. Calvinism is just the systematic application of this truth in all doctrine, piety, and life. If you make this truth your theological touchstone and resolve to reject everything that comes into conflict with it, and carry out that resolution consistently, you will find yourself a Calvinist.