No satisfactory way exists to explain how to form a good idea. You think about a problem until you're tired, forget it, maybe sleep on it, and then flash! When you aren't thinking about it, suddenly the answer arrives as a gift from the gods.  Of course, all ideas don't occur like that but so many do, particularly the most important ones. They burst into the mind, glowing with the heat of creation. How they do it is a mystery but they must come from somewhere. Let's assume they come from the "unconscious." This is reasonable, for psychologists use this term to describe mental processes which are unknown to the individual. Creative thought depends on what was unknown becoming known. All of us have experienced this sudden arrival of a new idea, but it is easiest to examine it in the great creative personalities, many of whom experienced it in an intensified form and have written it down in their life stories and letters. One can draw examples from genius in any field, from religion, philosophy, and literature to art and music, even in mathematics, science, and technical invention, although these are often thought to depend only on logic and experiment. All truly creative activities depend in some degree on these signals from the unconscious, and the more highly insightful the person is, the sharper and more dramatic the signals become. A type of creative experience is illustrated by the dreams which came to Descartes at the age of twenty-three and determined his life path. Descartes had unsuccessfully searched for certainty, first in the world of books, and then in the world of men. Then in a dream on November 10, 1619, he made the significant discovery that he could only find certainty in his own thoughts, cogito ergo sum ("I think; therefore, I exist"). This dream filled him with intense religious enthusiasm. Descartes' experience is representative of countless others in every field of culture. The unconscious is certainly the source of instinctive activity. But in creative thought the unconscious is responsible for the production of new organized forms from  ly disorganized elements. What point can we see in the example of Descartes ?
Dreams are the sources of instinctive activities. Dreams sometimes contribute to important discoveries. Geniuses have creative thoughts in their dreams. Important discoveries are always made in dreams.