If God exists, why can't I see Him?
Because He is a Spirit, and because no sinner could bear the sight of Him - yet He made Himself visible in Jesus, and those who trust Him will see His face.
You cannot see God because He is a Spirit, and because no sinful person could bear the sight of Him. But He has not left it there. He made Himself visible in Jesus Christ, and He has promised that those who trust Him will see His face.
This is not a question only unbelievers ask. Job, who believed in God with everything he had, said this in his suffering:
Behold, I go forward, but he is not there; and backward, but I cannot perceive him: On the left hand, where he doth work, but I cannot behold him: he hideth himself on the right hand, that I cannot see him
If you have looked for God and not found Him, you are in the Bible’s own company. The Bible does not treat the question as foolish. It answers it.
God is a Spirit.
God is a Spirit: and they that worship him must worship him in spirit and in truth.
He is not an object somewhere in the universe that you could locate with the right instrument. He is not the kind of thing eyes see.
And no sinner could bear the sight of Him.
Moses had found grace with God and spoke with Him as a friend:
for thou hast found grace in my sight, and I know thee by name.
Yet when Moses asked to see God’s glory, this was the answer:
And he said, Thou canst not see my face: for there shall no man see me, and live.
God then showed Moses what he could bear, and protected him while He did it:
I will put thee in a clift of the rock, and will cover thee with my hand while I pass by
Who only hath immortality, dwelling in the light which no man can approach unto; whom no man hath seen, nor can see
Isaiah was given a vision of the Lord on His throne. His first response was not comfort but terror - and then God did something for him:
Then said I, Woe is me! for I am undone; because I am a man of unclean lips, and I dwell in the midst of a people of unclean lips: for mine eyes have seen the King, the LORD of hosts. Then flew one of the seraphims unto me, having a live coal in his hand, which he had taken with the tongs from off the altar: And he laid it upon my mouth, and said, Lo, this hath touched thy lips; and thine iniquity is taken away, and thy sin purged.
That is the pattern: a sinner sees the holiness of God, knows at once that he cannot stand, and God Himself provides the cleansing. The distance between you and God is not only a matter of eyes. It is a matter of sin, and the Bible says so plainly:
Behold, the LORD’s hand is not shortened, that it cannot save; neither his ear heavy, that it cannot hear: But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear.
That is hard to hear. But it means the distance has a cause, and the cause can be dealt with - as it was for Isaiah.
So He made Himself visible.
Creation shows that God is - the heavens declare His glory, and the article “Does God really exist?” looks at that. But creation does not show you His face. For that, God did something further:
And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him.
One of Jesus’ disciples asked the very question you are asking:
Philip saith unto him, Lord, shew us the Father, and it sufficeth us. Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Shew us the Father?
This is also the answer to the objection that an invisible God is conveniently beyond checking. He was seen. The people who wrote about Him insisted on exactly that, and said why they were telling us:
That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, of the Word of life; (For the life was manifested, and we have seen it, and bear witness, and shew unto you that eternal life, which was with the Father, and was manifested unto us;) That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship is with the Father, and with his Son Jesus Christ.
Seen, looked upon, handled - and declared to you so that you could share what they found. And what the One they saw did for them, He did in love:
Unto him that loved us, and washed us from our sins in his own blood
Knowing Him without seeing Him
One of Jesus’ disciples refused to believe He had risen until he could see and touch Him. Jesus came to him:
Then saith he to Thomas, Reach hither thy finger, and behold my hands; and reach hither thy hand, and thrust it into my side: and be not faithless, but believing. And Thomas answered and said unto him, My Lord and my God. Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.
He was patient with Thomas. And He spoke a blessing over everyone who would believe without the sight Thomas was given - which is to say, over you. Peter wrote to people who had never seen Jesus and described what they had:
Whom having not seen, ye love; in whom, though now ye see him not, yet believing, ye rejoice with joy unspeakable and full of glory
It is possible to know Him and love Him now, without seeing Him. Millions do. John says the record of what Jesus did was written for exactly that purpose - so that people who were not there could believe.
You will see Him.
Everyone will see Christ when He returns:
Behold, he cometh with clouds; and every eye shall see him, and they also which pierced him: and all kindreds of the earth shall wail because of him.
And to those who are His, God has promised something more than seeing Him from afar:
Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not. Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.
and his servants shall serve him: And they shall see his face; and his name shall be in their foreheads.
So the question is not really whether you will ever see God. Every eye will. The question is whether you will see Him as His servant, and see His face - and that turns on what you do now with the One who came so that you could see Him.