James Mixon - Gen. 6:4 and Numbers 13:33 is a big problem for believers.
I would have to disagree. I am no Christian apologist as I am an atheist, and I in no way believe in an inerrant Bible. So keep that in mind as you will be reading this post.
Having that said, I don't think Gen. 6.4 and Num 13.33 are a contradiction. I mean, Genesis does say that the Nephilim died after the flood, and in Numbers 13 we do have a reference to those Nephilim as if they were still alive. However, keep in mind who mentions those Nephilim. To me, it seems that it was a purposeful lie on the part of the speakers (the spies who went off to the land with Caleb) to scare the Israelites so that they would not attempt to wage war against the Canaanites (and other nations.)
I mean, of course, I don't believe this even happened. I don't believe any of it is historical as we have evidence that the Israelites settled in the land of Canaan rather peacefully—without as many conflicts as the Old Testament "testifies." However, what I mean is that I don't think the author of Numbers made a contradiction. I believe the author of Numbers, when he was making up that story, mentioned the Nephilim purposefully, knowing that they were already dead in this fantasy world. I think that whoever wrote Numbers—and, no, it was not Moses—just wanted to add some drama into the story. So, as a result, we have spies who are deliberately lying to Moses and his people.
But let me highlight one thing again. I am an atheist, and I don't believe this account is even an actual historical fact. I'm just analysing it as I would a novel or any other creative piece of writing. It seems to me to be too obvious to actually consider it a contradiction.