When therefore Pilate heard this word he was more afraid, implying that John had seen all along that some element of "fear" had moved Pilate, and that now it was augmented. Superstition goes hand in hand with skepticism.
Instead of this being (as Keim says) contrary to psychologic laws, the history of skepticism is constantly presenting the same features (cf. Herod Antipas the Sadducee, who would dogmatically have repudiated the idea of resurrection, crying out concerning Jesus, "It is John the Baptist, whom I beheaded: he is risen from the dead," etc.
). We need not suppose that Pilate was suddenly affected by the truth of Jewish monotheism; but he may readily have believed that the wondrous Being before him was enshrouded in a mystery of supernatural portent and pretension that he could not fathom, and before which he trembled.
The idea of Divine energy enshrined in and wielded by human beings was not altogether foreign to heathen thought—and one centurion, at least, who was probably present on this very occasion, exclaimed that Jesus was a Son of God (Matthew 27:54).