The work by Paul Brunton is particularly good for this. Imagine you re in bed asleep and having a dream. The type of dream, pleasant or nightmarish, is irrelevant. In fact it is a very private world. People and places can either be familiar or not.
Themes can be familiar or completely absurd.
There may or may not be continuity. Now let s just think for a minute, when you re experiencing a dream it is quite obvious you are the dreamer, yet that strange world seems real enough for the short period of its duration. Of course they are figments of your imagination thrown together like chop suey. It means that when we are asleep our minds are very active creating, if you like, an alternative universe. And one I might add that is predisposed to our particular wants and wishes.