God gives knowledge of Christ and the Holy Spirit to those that reject it as well:

Romans 1:19 "since what may be known about God is plain to them, because God has made it plain to them."

The Holy Spirit also convicts unbelievers of sin:

John 16:7-11
"Nevertheless I tell you the truth. It is to your advantage that I go away; for if I do not go away, the Helper will not come to you; but if I depart, I will send Him to you. And when He has come, He will convict the world of sin, and of righteousness, and of judgment: of sin, because they do not believe in Me; of righteousness, because I go to My Father and you will see me no more; of judgment, because the ruler of this world is judged."

Light is given to all men:

John 3:19
"And this is the condemnation, that light has come into the world, and men loved darkness rather than light, because their deeds were evil."