Something being nonliteral doesn't mean it isn't reality; in fact, that is the point of metaphor, it uses a figure of speech so that people can understand an idealized scenario to comprehend the subtle truths inherent in complex real-life scenarios.To say, for instance, that Christ casting out demons is a metaphor/allegory/parable and in context scripture says it was/is reality. Parables as stories or examples of the truth in a given situation - again is not metaphor. I may tell you a story and leave out names and locals and some minutae but that doesn't mean the situation never really happened. It is the understanding of the truth that is prominent. If I misunderstood your direction on the subject in this thread - apologies. You seemed to be saying Jesus casting out demons was metaphor and that demons/evil spirits don't really exist, except as boogeymen. My past experience in real life and scripture refute what you are typing.
The use of idioms is essential to language, and these idioms are different for every language. When someone says they "heard it on the grapevine" they obviously don't mean they get their gossip from plants, it's a figure of speech.
Religious and philosophical literature is full of these phrases, unfortunately people seem to lose the understanding of the metaphor and begin to take the phrase as it seems. They'd be outside listening to grapevines trying to get the latest scoop because they don't know that it wasn't a literal phrase.
Using "demons" as a figure of speech is even still in use today, someone "battles their demons" and such. It is not at all unreasonable to apply this understanding to biblical use of it as well.
The demons do exist, but they are not satanic "beings" in the sense everyone here has portrayed i.e. that can act of their own volition and can control people or physical things. Demons are much like our metaphorical use of the word suggests, the dark, vicious tendencies that corrupt us humans. And I do believe Jesus "casts out" such evil. Just not a mystical bunch of apparitions that can hijack humans.
Feel free to disagree, of course This is how I understand it, not because of ignorance (I used to be very apologetic and have made every argument out there) but because this is most consistent with reason and objective reality.