Wall of fire

He drove out the man, and at the east of the garden of Eden he placed the cherubim and a flaming sword that turned every way to guard the way to the tree of life (Gen 3:24).

What are we supposed to visualize when we read Gen 3:24? In what sense did Eden have an entrance or exit? What did the seraph with the fiery sword look like? 

I've speculated on the topography of Eden. Perhaps it was a high river valley or fluvial island. Both might fit with the Mesopotamian locale (Gen 2:10-14).

But let's try come at it from another angle. The Pentateuch is a literary unit. To some degree, the books of the Pentateuch are mutually interpretive. That includes foreshadowing and backshadowing. So the The seraph with the fiery sword might be the same phenomenon as the pillar of fire in the wilderness. For instance:

And the Lord went before them by day in a pillar of cloud to lead them along the way, and by night in a pillar of fire to give them light, that they might travel by day and by night. The pillar of cloud by day and the pillar of fire by night did not depart from before the people (Exod 13:21-22).

Then the angel of God who was going before the host of Israel moved and went behind them, and the pillar of cloud moved from before them and stood behind them. It came between Egypt's camp and Israel's camp. Throughout the night the cloud brought darkness to the one side and light to the other side; so neither went near the other all night long (Exod 14:19-20). 

And in the morning watch the Lord in the pillar of fire and of cloud looked down on the Egyptian forces and threw the Egyptian forces into a panic (Exod 14:24).

And the Lord came down in a pillar of cloud and stood at the entrance of the tent and called Aaron and Miriam, and they both came forward (Num 12:5).

and they will tell the inhabitants of this land. They have heard that you, O Lord, are in the midst of this people. For you, O Lord, are seen face to face, and your cloud stands over them and you go before them, in a pillar of cloud by day and in a pillar of fire by night (Num 14:14).

And the Lord appeared in the tent in a pillar of cloud. And the pillar of cloud stood over the entrance of the tent (Deut 31:15).

There are clear similarities. The association of fire with angels. The defensive function of the fiery pillar. The parallel between the fiery figure before the entrance to Eden and the entrance to the tent of meeting. 

Mind you, that falls short of telling us what, exactly, the pillar of fire was. In the past, I've noted that descriptions of the pillar of fire and pillar cloud, especially in the desert setting, are reminiscent of desert devils in daytime and fire devils at night. A flaming tornado. 

I'm not suggesting that the pillar of fire is a merely natural phenomenon. It doesn't behave like an inanimate object. It has a stability and directionality unlike a desert devil or fire devil. So it might be a preternatural phenomenon. I don't think God is a shapeshifter like the heathen deity Proteus. But God can produce concrete phenomena that represent his presence. 

Or, if it's an angel in the usual sense, perhaps angels can assume the appearance of a desert devil or fire devil, performing a similar function. This would trade on natural symbolism but surpass what is naturally possible. And it would dovetail with the ambiguities of the burning bush. 

Perhaps, then, a wall of fire was blocking reentrance to the Garden of Eden. For that matter, maybe there was always a ring of fire around the Garden, excepting the entrance, to protect the Garden. A wall of fire encircling the Garden, as an impenetrable barrier to keep the tame animals inside and the wild animals outside. But when God expelled Adam and Eve, he sealed that off, so the Garden now had a continuous wall of fire on all sides. Or perhaps it has some other natural barrier.