Wow, @manbooks, you’ve had quite a conversation going on these last few weeks – interesting stuff! Although I’m late to the game, I’ll be glad to share a few thoughts.
I believe your original question was about whether someone who lived a righteous life could be saved without being a Christian.
That’s actually a hypothetical case that is, sadly, unrealistic. To live righteously enough to enter the presence of God without being consumed by His holiness would require that one be as absolutely holy as God Himself. Even Moses could not have done that in his mortal life (Exodus 33:20).
In fact, the angels who stand in His immediate Presence have two wings to hover in place on the surge of energy that flows ever outward from the throne, two wings to cover their feet against the burning coals that flow from beneath it, and two wings to cover their faces from the consuming glory of His holiness (Isaiah 6:1-7).
Someone being good enough to enter that Presence? It would take a miracle! (But hold that thought!)
Then you asked how people were saved before the cross. By faith, Abel offered a more excellent sacrifice than Cain (Hebrews 11:4ff). In fact, Hebrews 11 recounts many exploits that OT characters did by faith – and verse 13 says that they hadn’t received the promises (of the Messiah) in their day, but they saw them afar off by faith. So OT believers were saved by faith looking forward to the fulfilment of the gospel promise, just as we’re saved by faith looking back to it.
Ever since the fall, God had promised those first generations that a Seed would come of the woman (Genesis 3:15), Who would bruise the serpent’s head (a mortal blow) though it would bruise His heel in the process (a comparatively minor blow).
And God showed Adam and Eve an object lesson of how that would work by slaying innocent animals to take their death sentence (Genesis 3:21) – establishing the principle that for a guilty sinner to live, an innocent substitute must die. And God clothed them in the skins of those substitutes so that when He looked at them, He saw the innocence of the one who had died in their place. (I’m guessing those were sheep, based on what they themselves apparently taught Cain and Abel to do in chapter 4.)
Now, that was a very dim preview of the gospel of the Lamb of God who would take away the sin of the world – but it was all those first generations needed to respond in faith as Abel did in the next scene – and Cain refused to do. Those who believe are given the righteousness of the Lamb Who died in their place – the impossible, miraculous righteousness of God we mentioned at the start!
From that age to this, God has only required men to believe in whatever level of light He has entrusted to the world at that time. But the more gospel He reveals, the more He holds us accountable for.
He would later reveal to Abraham that the Promised Seed would be a descendant of his, and all the world would be blessed through Him. Abraham believed God and He counted it to him for righteousness (Genesis 15:6).
Of course, God has revealed much more gospel light by now, and all men are accountable to believe what’s been given – Acts 4:10-12. But you are right that in every age faith has come by hearing the word of God revealed to that generation.
You also asked about those who had never heard of Him. But even they have received light from God, and they’re accountable for the light they’re given. Romans 1:18-20 says that the light of creation clearly shows the reality of a Creator so that they are without excuse before Him.
Romans 2:14-15 says that the light of conscience likewise makes them accountable for the wrongs they’ve done. But verse 12 says that men are judged by the law they had, not by the law they didn’t. And Jesus said it would be more tolerable for those who violated less light than for those who violated greater – Matthew 11:20-24.
Your last question was about children who die before having a chance to believe. What we’ve said about the level of light applies here as well. Greater light, greater accountability; less light, less accountability; no light, no accountability. Infants would be those with no light whatsoever – not from the gospel, the creation or the conscience. Romans 4:15 says, where no law is, there is no transgression. Romans 5:13 says that sin is not imputed when there is no law. Such children would essentially be in a state of innocence no different from Adam and Eve before the fall. They’re not “lost” yet.
I hope these thoughts are helpful to you!