Some common synonyms of illusion are delusion, hallucination, and mirage. While all these words mean "something that is believed to be true or real but that is actually false or unreal," illusion implies a false ascribing of reality based on what one sees or imagines. Link
From the definition above, we can see that illusion is a false representation of the real thing. I am of the opinion that illusion has to do with the state of the mind because other folks might not see what you are seeing, they might not agree with you. So you are the only one with the opinion of what you claim to see.
Well, I know that illusion cannot work forever. One way or another, the truth will come to light. It is only a matter of time before the truth comes to light. So, I will say illusion is basically on a temporal basis not long term. And illusion is not the real deal, it is a means to an end. You create an illusion maybe as a distraction to get something else done, it is not an end in itself.
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