I am very glad that you are inquisitive to know the science of Krsna consciousness and you are already practically experiencing the awakening of transcendentally blissful love of God Krsna by the simple chanting of His Holy Names. This awakening of pure love of God is the ultimate perfection of all bona fide religious principles including Christian, Judaic, Mohammedan, Hindu, etc. Just as it is recorded that Lord Jesus Christ said that the first commandment is that one should love God with all his heart, and soul and mind. Similarly Krsna instructs that everyone should surrender unto Him in Love. Lord Jesus says that the first thing is to develop your love for God. Krsna is God. Krsna says to love Him only. So what is the difference between the original teachings of Lord Jesus Christ and Krsna?
Yes, it is a fact that no one can see Krsna without being a pure devotee of the Lord. Every living entity is the son of god, but not all of the sons are faithful to their Father. This is explained in Bhagavad Gita. So one who turns away from his father naturally cannot see his father; but the faithful son can see his father at any time. Under the circumstances, we can understand the word of John because amongst all the people of that place Jesus Christ was the only faithful son of God, Krsna. Lord Jesus says (John 6:46), "Not that any man hath seen the father, save he which is of God, he hath seen the Father." So one who is a devotee of the Lord in pure love, who teaches others how to love God is the messenger of God and he can see God without any doubt. Lord Krsna says in Bhagavad Gita (11:54), "My dear Arjuna, only by undivided devotional service can I be understood as I am, standing before you; and I can thus be seen directly. Only in this way can you enter into the mysteries of my understanding." So the method of approaching God, bhaktiyoga or devotional service, and the supreme goal of life, pure love of Krsna, is the same message taught by Lord Jesus Christ as well as Krsna Himself. The matter is very simple: Lord Jesus is the faithful son of God and his Father God is Krsna, so there cannot be any disagreement between them. Therefore the Father and Son are one, in agreement.