1. Yes, our spirit is able to detect the Spirit of God within.
Rom 8:16 The Spirit itself beareth witness with our spirit , that we are the children of God:
2. It is the Spirit of God within believers which reveals spiritual things via the spirit within man.
1 Cor 2:11 For what man knoweth the things of a man, save the spirit of man which is in him? even so the things of God knoweth no man, but the Spirit of God.
3. True born again believers actually KNOW that they have been saved.
1 John 5:13 These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
4. Atheists and God haters have rejected God revelations of Himself through the things He created.
19 Because that which may be known of God is manifest in them; for God hath shewed it unto them.
20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
21 Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
22 Professing themselves to be wise, they became fools,