Sherlock Helms, a budding YouTube Calvinist, produces this video on the Perseverance of the Saints:

In the video, Helms claims John 6:37-39 describes this “Perseverance of the Saints” in which people are magically stopped from turning away from God:

Joh 6:37 All that the Father gives Me will come to Me, and the one who comes to Me I will by no means cast out.
Joh 6:38 For I have come down from heaven, not to do My own will, but the will of Him who sent Me.
Joh 6:39 This is the will of the Father who sent Me, that of all He has given Me I should lose nothing, but should raise it up at the last day.

But Jesus, in spite of John 6:39, Jesus did lose one. This is explicit in John 17:12:

Joh 17:12 While I was with them in the world, I kept them in Your name. Those whom You gave Me I have kept; and none of them is lost except the son of perdition, that the Scripture might be fulfilled.

Did Jesus lose none that the father sent him, as per John 17:12? The answer is no. Judas was lost. The text explains why this one was lost, but it is still a loss. People “being kept” is not some sort of spiritual enabling that overcomes their human nature. Instead, it is something that can be undone.

So, what then does it mean “none of them is lost”? Contextually, it looks like none of Jesus’ followers were killed during his ministry. Contextually, this is a task for Jesus (“I kept them in your name”). This is not about keeping them spiritually for salvation. This is also not about some spiritual property that stops people from rebelling against God. Instead, this is an activity that Jesus did for his followers while he was on Earth.

In any case, John 17:12 is a fulfillment of John 6:37. There is no need to assume this is applicable to today, and no need to assume onto it any Calvinist notion of perseverance of the saints.