This might be a topic having already been discussed but, the famous phrase "there shall be weeping and gnashing of teeth" has usually been understood to mean that there is a "conscious literal torment" in literal fire. I always assumed the same when I was in ET. But when Christ uses the phrase "gnashing of teeth" I submit that it does not suggest a gritting of teeth due to physical pain or torture. Rather, the term is a figure of speech meaning to be mocking, or to be set against. Here are more examples from the OT:
16 Like the ungodly they maliciously mocked; they gnashed their teeth at me.
God assails me and tears me in his anger and gnashes his teeth at me; my opponent fastens on me his piercing eyes.
16 All your enemies open their mouths wide against you; they scoff and gnash their teeth and say, "We have swallowed her up. This is the day we have waited for; we have lived to see it."
In Christ's parables, he says that there shall be "gnashing of teeth" in the "outer darkness." But, Christ himself also says that "men love the darkness" and they do not come into the light, for fear that their wicked works will be exposed. I believe that when anyone is cut off from the blessings of Life (the Spirit) "gnashing of teeth" is an expression for the way that the carnal man is set against God in his nature. I believe that the Prodigal Son gnashed his teeth against God's way for a while in his own actions, his sin, not literally because he was being tortured.
Paul warned "God will not be mocked." Another way of saying that is that God will not allow people to gnash their teeth at him by trodding under foot the son of God through willful sinning. I believe that God's method to deal with that, is to allow the sin to naturally bring them to a low place and thus to lead them to repentance.