Oneiromancy
If you could interpret a dream to foretell the future, and if you could know what lay ahead, the question is could you change it?Or if you could see what your future is precisely in your dreams, could you change it?
If you can change it, you wouldn't dream it in the first place.
If you compile all your dreams in a book, how many of those came true? And how many of those had symbolic meaning that you realized their significance later on in life.
If you ever had a fulfilling dream or a dream with symbolism that came true, then that means the future already exists, and if the future exists, then the nature of our free will is questionable.