John’s further statement that Jesus is the atoning sacrifice, not only for “our” sins, but also for those of the whole “world” (κόσμος), is sometimes used to support the idea of universalism—that is, that everyone in the world will be saved by Christ’s atoning sacrifice, apparently whether they know it or not. But such a thought ignores both the historical context of the book and the particular use of kosmos in the Johannine corpus (cf. John 3:16, which presupposes the death of Jesus and consequent forgiveness of sins). One response to claims of universalism is to argue that Christ’s death is sufficient to atone for the sins of the whole world, even if only those who actually come to faith in him are saved from their sin. While that may be true, as John Calvin acknowledges, it is not what John is saying here. If here it is a reference to the whole planet, consideration of the historical context in which John wrote makes a more likely interpretation to be the universal scope of Christ’s sacrifice in the sense that no one’s race, nationality, or any other trait will keep that person from receiving the full benefit of Christ’s sacrifice if and when they come to faith.
In the ancient world, the gods were parochial and had geographically limited jurisdictions. In the mountains, one sought the favor of the mountain gods; on the sea, of the sea gods. Ancient warfare was waged in the belief that the gods of the opposing nations were fighting as well, and the outcome would be determined by whose god was strongest. Against that kind of pagan mentality, John asserts that the efficacy of Jesus Christ’s sacrifice is valid everywhere, for people everywhere, that is, “the whole world.” The Christian gospel knows no geographic, racial, ethnic, national, or cultural boundaries.
But “world” in John’s writings is often used to refer not to the planet or all its inhabitants, but to the system of fallen human culture, with its values, morals, and ethics as a whole. Lieu explains it as that which is totally opposed to God and all that belongs to him. It is almost always associated with the side of darkness in the Johannine duality, and people are characterized in John’s writings as being either “of God” or “of the world” (John 8:23; 15:19; 17:6, 14, 16; 18:36; 1 John 2:16; 4:5). Those who have been born of God are taken out of that spiritual sphere, though not out of the geographical place or physical population that is concurrent with it (John 13:1; 17:15; see “In Depth: The ‘World’ in John’s Letters” at 2:16).
Rather than teaching universalism, John here instead announces the exclusivity of the Christian gospel. Since Christ’s atonement is efficacious for the “whole world,” there is no other form of atonement available to other peoples, cultures, and religions apart from Jesus Christ. As Calvin comments:
Therefore, under the word “all” he does not include the reprobate, but refers to all who would believe and those who were scattered through various regions of the earth. For, as is meet, the grace of Christ is really made clear when it is declared to be the only salvation of the world.[1]
[1] Jobes, K. H. (2014). 1, 2, & 3 John. (C. E. Arnold, Ed.) (p. 80). Grand Rapids, MI: Zondervan.