John 12:40 (ESV) — 40 “He has blinded their eyes and hardened their heart, lest they see with their eyes, and understand with their heart, and turn, and I would heal them.”To repeat myself: The subjunctive mode given in the negative designates purpose—not implication that the negative is actually possible.
iva (lest) conjunction of adverbial purpose
it makes no sense purposing to prevent something which is not possible
especially when it is God who is purposing