Also spelled "Apokatastasis."
Apocatastasis (literally, the restoration of all) is the teaching that everyone will, in the end, be saved. It looks toward the ultimate reconciliation of good and evil; all creatures endowed with reason, angels and humans, will eventually come to a harmony in God's kingdom.
For Origen, this explicitly included the devil. In effect, Apocatastasis denies the final reality of hell, and interprets all Biblical references to the "fires of hell" not as an eternal punishment, but a tool of divine teaching and correction, akin to purgatory.
In the twentieth-century, this doctrine was reinvigorated especially by Hans Urs von Balthasar, who, in his book Dare We Hope “That All Men Be Saved