In his introductory essay to John Owen’s The Death of Death in the Death of Christ, J. I. Packer writes that Calvinism and Arminianism are “two coherent interpretations of the biblical gospel, which stand in evident opposition to each other. The difference between them is not primarily one of emphasis, but of content.”
Packer continues, (paragraphing added)
One proclaims a God who saves; the other speaks of a God who enables man to save himself.
One view presents the three great acts of the Holy Trinity for the recovering of lost mankind—election by the Father, redemption by the Son, calling by the Spirit—as directed towards the same persons, and as securing their salvation infallibly.
The other view gives each act a different reference (the objects of redemption being all mankind, of calling, those who hear the gospel, and of election, those hearers who respond), and denies that any man’s salvation is secured by any of them.
The two theologies thus conceive the plan of salvation in quite different terms.
One makes salvation depend on the work of God, the other on a work of man; one regards faith as part of God’s gift of salvation, the other as man’s own contribution to salvation; one gives all the glory of saving believers to God, the other divides the praise between God, who, so to speak, built the machinery of salvation, and man, who by believing operated it.
Plainly these differences are important, and the permanent value of the “five points,” as a summary of Calvinism, is that they make clear the points at which, and the extent to which, these two conceptions are at variance.