Which two statements from the passage best illustrate the central ideas? Before the dawn of history mankind was engaged in the study of dreaming.

To use Professor Bergson's striking metaphor, our memories are packed away under pressure like steam in a boiler and the dream is their escape valve.

But the psychologist rarely paid attention to dreams except incidentally in his study of imagery, association and the speed of thought.

The subject of the significance of dreams, so long ignored, has suddenly become a matter of energetic study and of fiery controversy the world over.

For we know that the study of the stars, though undertaken for selfish reasons and pursued in the spirit of charlatanry, led at length to physical science, while the study of dreams has proved as unprofitable as the dreaming of them.