Theophylact of Ohrid

Others, understanding somewhat, said: "These are not the words of one possessed by a demon." Since the Lord could not shut their mouths with words (for even the reasonable ones neither fully understood His words themselves, nor would they have convinced their opponents), they attempt to defend Christ by deeds and say that these are not the words of one possessed by a demon. Where then is this evident from? From the deeds. Can a demon open the eyes of the blind? And if this deed is divine, then the words are surely likewise.

Commentary on John ↗

Thomas Aquinas

This opinion is refuted by the statements of the other side, and this is in two ways. First, by the profundity of Christ's words. Thus he says, Others, that is, those who rightly understood, said, These are not the sayings of one who has a demon. This was like saying: It is clear from what he is saying that he is not mad, because his words are orderly and profound: "Lord, to whom shall we go? You have the words of eternal life" (6:69). …

Commentary on John ↗

Bonaventure

"Others were saying: These are not the words of one having a demon": these were beginning to be illuminated in some way, whence they take refuge in the miracle of illumination: "Can a demon open the eyes of the blind?" Chrysostom: "Because they could not shut their mouths with words, they made their demonstration from works"; whence works give credence to words; therefore below in the same chapter: "And if you do not believe me, believe the works."

Commentary on John, Chapter 10 ↗