33 After many dark sayings, spoken in parables by Him Whom they already knew as the Christ foretold by Moses and the Prophets, Whom Nathanael had confessed as the Son of God and King of Israel, Who had Himself reproached Philip, in his question about the Father, for not perceiving, by the works which He did, that the Father was in Him and He in the Father; after He had already often taught them that He was sent from the Father; still, it was not till they had heard Him assert that He had gone forth from God that they confessed, in the words which immediately follow in the Gospel— His disciples say unto Him, Now do You speak plainly, and speakest no proverb.
Now therefore we are sure that You know all things, and needest not that any man should ask You; by this we believe that You went forth from God. What was there so marvellous in this form of words, Went forth from God, which He had used? Had ye seen, O holy and blessed men, who for the reward of your faith have received the keys of the kingdom of heaven and power to bind and to loose in heaven and earth, works so great, so truly Divine, wrought by our Lord Jesus Christ, the Son of God; and do ye yet profess that it was not until He had first told you that He had gone forth from God that you attained the knowledge of the truth?
And yet ye had seen water at the marriage turned into the marriage wine; one nature becoming another nature, whether it were by change, or by development, or by creation. And your hands had broken up the five loaves into a meal for that great multitude, and when all were satisfied ye had found that twelve baskets were needed to contain the fragments of the loaves; a small quantity of matter, in the process of relieving hunger, had multiplied into a great quantity of matter of the same nature.
And ye had seen withered hands recover their suppleness, the tongues of dumb men loosened into speech, the feet of the lame made swift to run, the eyes of the blind endowed with vision, and life restored to the dead. Lazarus, who stank already, had risen to his feet at a word. He was summoned from the tomb and instantly came forth, without a pause between the word and its fulfilment. He was standing before you, a living man, while yet the air was carrying the odour of death to your nostrils.
I speak not of other exertions of His mighty, His Divine powers. And is it, in spite of all this, only after ye heard Him say, I went forth from God, that you understood Who He is that had been sent from heaven? Is this the first time that the truth had been told you without a proverb? The first time that the powers of His nature made it manifest to you that He went forth from God? And this in spite of His silent scrutiny of the purposes of your will, of His needing not to ask you concerning anything as though He were ignorant, of His universal knowledge? For all these things, done in the power and in the nature of God, are evidence that He must have gone forth from God.
Source: On the Trinity (New Advent)