18 No one has seen God at any time. The only begotten Son, who is in the bosom of the Father, He has declared Him.
Verse 18 is yet another assertion of Christ’s deity. John began and ended the prologue by bracketing it with the deity of Christ.
18 No one has seen God [emphatic] at any time.
Note that even Moses did not see God’s undiminished glory (Ex 33:18). God’s undiminished glory is the totality of His essence. Finiteness is incapable of seeing infiniteness.
The Greek is extremely emphatic that no one has seen God at any time. This is an undeniable fact. No one has seen God’s complete essence. We can see a manifestation of God, such as a physical appearance of God (theophany), but not His essential nature. God is pure spirit, so human faculty cannot see Him (Ex 33:20; 1 Ti 6:16; 1 Jn 4:12).
There is no definite article “the” before the word “God.” This is the same situation we found in verse 1. Because there is no “a” or “an” in the Greek, the word here emphasizes quality, or God’s essence.
The Word came to manifest who and what God is because we cannot see His total essence.
No one can see God’s undiminished glory or by searching find His fullness (Jn 5:37; 6:46; 1 Ti 1:17; Job 11:7). Jesus, however, saw His undiminished glory (Jn 6:46). In Christ, we do not see God’s absolute essence but His revelation in Jesus Christ.