John elaborates, saying, "Therefore they could not believe, as Isaiah said: 'I have blinded their eyes and hardened their hearts, that they should not see with their eyes, nor understand with their hearts, nor be converted, and I should heal them'" (John 12:39-40). This seems to contradict the prior assertion that they would not see at all. It is worth noting, though, that the statement regarding their inability to see is definitive: "that they should not see with their eyes." It is made clear in saying, "Wherefore they could not believe." This indicates that the blinding was not intended to prompt them towards repentance, as belief is necessary for conversion and healing; rather, they were blinded because of their unbelief.
If this interpretation holds, who would argue on behalf of the Jews, suggesting their guilt is lessened because of their inability to believe? For their eyes were blinded due to their inability to believe. However, we must recognize God's innocence in this matter. It must also be acknowledged that their blinding was a consequence of their sins, yet it was this very blinding that hindered their faith. John's assertion stands: "Therefore they could not believe because he had blinded their eyes" (John 12:39-40).
Thus, our attempts to comprehend their blinding as a catalyst for conversion are in vain; they could not convert because they did not believe, and they could not believe due to their blindness. Some among the Jews might have been open to healing. However, their pride rendered initial disbelief necessary, leading to a blindness that kept them from understanding the Lord's teachings through parables. As a result, they failed to recognize Him and ultimately participated in His crucifixion. After His Resurrection, humiliated by their actions and the judgement that followed, they would come to love the One who offered them forgiveness. Their pride was so immense that only through significant humiliation could they be transformed.
One may question the clarity of this understanding unless they read further in the Acts of the Apostles, where there is harmony with John's assertion of their inability to believe due to the blinding of their eyes. Hence, we see the reasoning behind their blindness: it served to obscure their understanding of the Lord's words communicated through parables. Following Christ's Resurrection, they would be prompted toward a deeper repentance and through this receive mercy for their obedience, ultimately fostering a fervent love.
Concerning those who were not aided by this blinding in their conversion, the prophet speaks of them elsewhere, as mentioned by the apostle in reference to the obscurity of tongues: "I will speak to this people in other tongues and with other lips, and so they will not hear me, saith the Lord" (1 Cor. 14:21; Isaiah 28:11). It is clear that this pronouncement serves a purpose; it encourages the humble acknowledgment of sin and an earnest pursuit of God. This mirrors the practice in physical medicine, where treatments often cause initial discomfort in order to promote healing. Eye ointments, for example, can only take effect if they first obscure vision.
Moreover, the prophet asserted, "Unless ye believe, ye shall not understand" (Isaiah 7:9). This might appear to conflict with John's statement that they could not believe because their eyes were blinded (cf. John 12:40). However, the connection lies in the nature of belief and understanding; one must believe to grasp the divine truths He offers. If comprehension is lacking, belief becomes impossible. What has been declared must be comprehended to facilitate belief, while faith serves to illuminate what remains obscure.