Accountability, Seeing Miracles, and the Israelites in the Wilderness

As I've done my daily quiet time in the Book of Deuteronomy, I've thought about a view that one of my relatives has.  According to my relative, people in this day and age can be saved, but they cannot be lost.  Why?  Because there is not enough unassailable evidence that Christianity is the one true religion for God to judge people according to their response to it.  In the Bible, particularly the New Testament, my relative notes, miracles accompany the proclamation of the Gospel in order to attest to the Gospel's truth (see John 15:24; Hebrews 2:4).  When miracles do not accompany the preaching of the Gospel, however, how can God judge people for rejecting it?  On what basis should people believe in the Gospel as opposed to other religions and philosophies, if God does not prove to them beyond a reasonable doubt that the Gospel is true?

A number of my evangelical friends say that the people who reject the Gospel would probably reject it even if they saw a miracle (see Luke 16:31), but I have issues with that claim.  So people should be judged according to a hypothetical----according to what they would have done?  That makes no sense to me.
So what's this have to do with Deuteronomy?  I read Deuteronomy 1, and it talks about how the Israelites were barred from the Promised Land because of their unbelief.  They were intimidated by the walls of Canaan and the size of the Amorites, and thus they did not want to attempt to conquer Canaan.  I wondered if God likewise judges me when I am afraid, but then I saw that the Israelites in Deuteronomy 1 had advantages that I myself do not have.  As Deuteronomy 1:30-33 indicates, the Israelites had seen and experienced God's power: God's deliverance of Israel from Egypt, God taking care of the Israelites in the wilderness, and God guiding the Israelites by cloud and by fire.  I haven't seen miracles at that level, so, while I can understand God judging the Israelites of that time for being afraid, I have a hard time believing that God judges me for my fear.

Some may argue that God does judge people in the here and now, as God judged the Israelites in the wilderness, for the wilderness generation are paraded before New Testament Christians as an example.  After all, does not the Epistle to the Hebrews warn its Christian audience not to be unbelieving, as were the Israelites in the wilderness, lest they fail to enter God's rest?  And does not Paul in I Corinthians 10 exhort the Corinthians not to be like the sexually-immoral Israelites in the wilderness?  Does not that imply that the lessons of Deuteronomy 1 are for all time, and apply even to those who have not seen God's miracles?

But it can be argued that the Hebrews and the Corinthians, too, saw and experienced miracles.  Hebrews 6:10 refers to people who have tasted the powers of the World to Come.  And I Corinthians 12:28 mentions miracles and the gift of healing.

So is the Bible irrelevant, if people are not held accountable over whether or not they believe in it?  I don't think so.  It has good principles.  I think of the hyper-dispensationalist saying that I've heard that parts of the Bible are for us, but they were not written to us.  For example, I know of hyper-dispensationalists who do not believe that (say) all of the Gospel of Matthew is normative for Christians today, for they maintain that the Gospel of Matthew teaches a works-salvation, whereas Christians are saved by grace through faith.  But they still study the Gospel of Matthew because they believe that it has edifying stuff, even for them.  Similarly, while I am not in the same position as the Israelites in the wilderness or even the early church, I can still be edified by lessons pertaining to them: how we can trust God because he loves us and wants to take care of us, for example.

I should say this about accountability: I do not want to imply that human beings in the here-and-now are not accountable to God for what they do.  The issue that I'm addressing is salvation: when does God hold people accountable for how they respond to the Gospel?  How much knowledge do they need before they indeed are held accountable?  Of course, one can point out that morality and salvation are intertwined issues, for salvation is God saving us from the punishment that we deserve for our immorality.  So things are thornier than I may think.