What are we to make of this?
In terms of Jesus taking upon Himself the sins of the world, 4-Point Calvinist, William MacDonald, explains: “...by His death on the cross, the Lord bought the world and all who are in it. But He did not redeem the whole world. While His work was sufficient for the redemption of all mankind, it is only effective for those who repent, believe, and accept Him.” (Believer’s Bible Commentary, p.2295)
MacDonald adds: “The NT distinguishes between purchase and redemption. All are purchased but not all are redeemed. Redemption applies only to those who receive Jesus Christ as Lord and Savior, availing themselves of the value of His shed blood (1 Pet. 18, 19).” (Believer’s Bible Commentary, p.2295)
Additionally, 5-Point Calvinist, R.C. Sproul, sums up the atonement views of his theological rival: “Historic Arminianism embraces particularism: not all people are saved, only a particular number of them. That particular group of people who are saved are those who respond to the offer of the gospel with faith. Only those who believe appropriate the benefits of the saving atonement in Christ.” (What is Reformed Theology, p.165)
To me, this seems right in line with Jesus' own analogy of Calvary, as told to Nicodemus at John 3:14-15, as it pertains to Numbers 21:6-9.
However, Sproul also warns: “What would have happened to the work of Christ if nobody believed in it? That had to be a theoretical possibility. In this case Christ would have died in vain.” (What is Reformed Theology, p.167)
How could that be a "theoretical possiblity," when yet at the very moment that Jesus was on the Cross of Calvary, Abraham's Bosom (as per Luke 16:19-31) was already full of the OT Saints? And what of all those who were alive and believed in Jesus during His earthly ministry? Did Sproul simply slip up in his logic?