will not and cannot

Joseph Fielding Smith: They [those that commit the unpardonable sin] reach a condition where they will not and cannot repent. The spirit of murder fills their hearts and they would, if they had the power, crucify our Lord again, which they virtually do by fighting his work and seeking to destroy it and his prophets.

(Book: "Doctrines of Salvation," vol. 1. p. 49)