Monergism

So far from magnifying the love and grace of God, this claim dishonors both it and Him, for it reduces God's love to an impotent wish and turns the whole economy of "saving" grace, so-called ("saving" is really a misnomer on this view), into a monumental divine failure. Also, so far from magnifying the merit and worth of Christ's death, it cheapens it, for it makes Christ die in vain. Lastly, so far from affording faith additional encouragement, it destroys the Scriptural ground of assurance altogether, for it denies that the knowledge that Christ died for me (or did or does anything else for me) is a sufficient ground for inferring my eternal salvation; my salvation, on this view, depends not on what Christ did for me, but on what I subsequently do for myself. Thus, this view takes from God's love and Christ's redemption the glory that Scripture gives them, and introduces the anti–scriptural principle of self-salvation at the point where the Bible explicitly says: "not of works, lest any man should boast." You cannot have it both ways: an atonement of universal extent is a depreciated atonement. It has lost its saving power; it leaves us to save ourselves. The doctrine of the general ransom must accordingly be rejected, as Owen rejects it, as a grievous mistake. By contrast, however, the doctrine which Owen sets out, as he himself shows, is both biblical and God–honoring. It exalts Christ, for it teaches Christians to glory in His Cross alone, and to draw their hope and assurance only from the death and intercession of their Saviour. It is, in other words, genuinely Evangelical. It is, indeed, the gospel of God and the catholic faith.
J.I. Packer An Introduction to John Owen's Death of Death in the Death of Christ

This is the most controversial of the five [points of Calvinism], because of Bible passages apparently teaching that Christ died for every individual. See, for example, 2 Cor. 5:15, 1 Tim. 4:10, 1 John 2:2. There are "universal" dimensions of the atonement: (a) it is for all nations, (b) it is a recreation of the entire human race, (c) it is universally offered, (d) it is the only means for anyone to be saved and thus the only salvation for all people, (e) its value is sufficient for all. Nevertheless, Christ was not the substitute for the sins of every person; else, everybody would be saved. For the atonement is powerful, efficacious. It does not merely make salvation possible; rather it actually saves. When Christ "dies for" somebody, that person is saved. One of the apparent "universal atonement texts," 2 Cor. 5:15, makes that point very clearly. Thus he died only for those who are actually saved. The biblical concern here is more with the efficacy of the atonement than with its "limitation;" perhaps we should call it "efficacious atonement" rather than "limited atonement," and, having then lost the TULIP, develop through genetic engineering a flower we could call the TUEIP. But of course efficacy does imply limitation, so limitation is an important aspect of this doctrine.
John Frame