So those who don't believe in God because he hasn't deigned to reveal himself to them, can't be held to blame for their non belief. What, then, do we make of Hell?
It is not the Lord's desire that any should perish,
but that all men would come to repentance.
But the sad truth is very few will come to repentance, and if not for God's mercy none would even be saved. But God knows before hand who will repent, and who will believe on Him when called, and by that foreknowledge God also knows those whom He has chosen to reveal Himself to.
Romans 9:18-23
King James Version (KJV)
18 Therefore hath he mercy on whom he will have mercy, and whom he will he hardeneth.
19 Thou wilt say then unto me, Why doth he yet find fault? For who hath resisted his will?
20 Nay but, O man, who art thou that repliest against God? Shall the thing formed say to him that formed it, Why hast thou made me thus?
21 Hath not the potter power over the clay, of the same lump to make one vessel unto honour, and another unto dishonour?
22 What if God, willing to shew his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction:
23 And that he might make known the riches of his glory on the vessels of mercy, which he had afore prepared unto glory,