Summary: John 1:18 clearly defines Jesus as God the Son who reveals God the Father.
“The Invisible One Explained”
John 1: 1 In the beginning was the Word, and the Word was with God, and the Word was God. 2 He was in the beginning with God. 3 All things came into being through Him, and apart from Him nothing came into being that has come into being. 4 In Him was life, and the life was the Light of men. 5 The Light shines in the darkness, and the darkness did not comprehend it.
6 There came a man sent from God, whose name was John. 7 He came as a witness, to testify about the Light, so that all might believe through him. 8 He was not the Light, but he came to testify about the Light. 9 There was the true Light which, coming into the world, enlightens every man. 10 He was in the world, and the world was made through Him, and the world did not know Him. 11 He came to His own, and those who were His own did not receive Him. 12 But as many as received Him, to them He gave the right to become children of God, even to those who believe in His name, 13 who were born, not of blood nor of the will of the flesh nor of the will of man, but of God.
14 And the Word became flesh, and dwelt among us, and we saw His glory, glory as of the only begotten from the Father, full of grace and truth. 15 John testified about Him and cried out, saying, "This was He of whom I said, 'He who comes after me has a higher rank than I, for He existed before me.' " 16 For of His fullness we have all received, and grace upon grace. 17 For the Law was given through Moses; grace and truth were realized through Jesus Christ. Here is the emphatic conclusion to the Prologue of the Gospel of John TODAY: 18 “No one has seen God at any time; the only begotten God who is in the bosom of the Father, He has explained Him.”
(Here is the text the way it is appears in the Greek: “God no one has seen NEVER; an only begotten God the One being into the bosom of the Father that One (and no other) declared.”)
“No one has ever seen God” is an extremely emphatic statement, and in the original text, “God” is placed at the beginning of the sentence as the subject. (It would read: “God (that is, God as God, in His being, no one has seen NEVER.”) The double negative of “no one” and “never” makes it clear that absolutely no one has ever seen God in His Being or God as God in his complete essence and fullness at any time, except the Son. It presents a stark familiarity and reminder of John1:1-2: “In the beginning was the Word, and the Word was with God, and the Word was God. 2 He was in the beginning with God.” The Word who was always with God in the beginning and the Word who was always God, affirms the essential deity of the Lord Jesus Christ.
Jesus would later affirm this part of the verse in John 5:37: "And the Father who sent Me, He has testified of Me. (The Father is the witness of the Son.) You have neither heard His voice at any time nor seen His form.” God is spirit and cannot be perceived by human eyes.