Weak Support for A Positive Principle/Law of Hermeneutics
Let's expand the context just a bit, especially since my form of hermeneutics primarily uses the Scriptures themselves in conjunction with common language to discern meaning. So John 7:14-19 (KJV):
14 Now about the midst of the feast Jesus went up into the temple, and
taught. 15 And the Jews marvelled, saying, How knoweth this man
letters, having never learned? 16 Jesus answered them, and said, My
doctrine is not mine, but his that sent me. 17 If any man will do his
will, he shall know of the doctrine, whether it be of God, or whether
I speak of myself. 18 He that speaketh of himself seeketh his own
glory: but he that seeketh his glory that sent him, the same is true,
and no unrighteousness is in him. 19 Did not Moses give you the law,
and yet none of you keepeth the law? Why go ye about to kill me?
Some Commentary on the Passage
v.14 Jesus is teaching in the Temple.
v.15 The Jews do not understand how Jesus can know anything about the Scriptures, having never studied the OT under the Jewish Rabbis there in the Temple.
v.16 Jesus replies to them that His doctrine is not made up, but rather He is the messenger of another. This implies that His doctrine was perceived as being made up. They were suspicious when stating the question of v.15 because He had not trained under them. As v.12 notes (not quoted above), they believed He was deceiving the people.
v.17 Jesus here ties obedience to knowing whether what Christ is teaching is true (not interpreting what He is teaching). This is clarified in v.18-19.
v.18 His statement here is not a general truth (that is, if random person Sam glorifies some other person Jim, Sam is not necessarily automatically speaking truth), but a specific statement Christ is making about Himself and His teaching of God. If Christ is seeking God's glory, who is the one Who sent Him, then Christ cannot help but be speaking truth, because only God is true, and He can only be glorified by truth.
v.19 But the Jews were not even being obedient to the truth they had, the Law of Moses. So what justification did they have to seek Jesus' death (referring back to v.1 of chapter 7, and later v.25)? None. And they certainly were not going to believe anything new Jesus might be saying, when they did not even believe what Moses said.
Back to Hermeneutics
Jesus is building his argument by asserting that they already know (intellectually) the doctrine of God in the law of Moses. They know what the law says. But they are not obeying it. He later affirms they know Who He is ("Ye both know me, and ye know whence I am," v.28), but do not believe. This all hinges on that they really do not know (personally) God ("whom ye know not," v.28), else they would have been obedient.
Hermeneutics is about the intellectual understanding of what the text says, and the arguments it makes toward conclusions. That is needed before the personal understanding of the text's significance to the reader can be discerned. One must understand language before one can obey a command; likewise, one must understand Scripture before one can be obedient to it.
So v.17 is saying that they are intentionally blinding themselves to the truth of what Christ is proclaiming by their willful disobedience to the prior revelation, Mosaic law (v.19), already understood.
This shows a negative principle at work--if one rejects previous truth, later truth will be opaque to them (truth builds upon truth).
But it does not affirm a positive principle. Just because one is obedient does not mean they will necessarily gain understanding (the realm of hermeneutics) of what the Scripture says. But they will trust that what is interpreted to be stated is true and applicable to God's plan (and possibly that individual).
This is not to say the Spirit will not help one find the resources needed to have understanding, but He will not just zap one with understanding without some education behind it—learning language, history, culture, etc. The Spirit can and does help even the disobedient to understand as well (else no one would ever pass from disobedience to obedience, because they would never understand what it is they are to obey).