The dreams which we remember and are able to describe are those which occur just as we are falling asleep or just as we are beginning to awaken. It is during these times that our conscious mind is partially active and in a state to receive impressions which are retained by the memory. Frequently, however, these impressions are so faint that they are remembered only for a short time. We may remember a dream for a few minutes when we wake up in the night, but the next day, it is entirely forgotten. On the other hand, there are dreams which are so vivid, and which impress themselves so very strongly upon us, that we can recall them and describe them in detail years afterwards.

During sleep, this mysterious underworld of thoughts comes into control, and because it is unbounded either by time or space, it can reveal to us conditions of our present and future state of which we have no knowledge when we are awake and wholly conscious.

That "dreams go by opposites" is a general belief which is sometimes doubted. With certain qualifications, however, it is a perfectly true statement, although it is only recently that the reason for this has been discovered. There is one peculiarity about the subconscious mind which particularly distinguishes it from the conscious. When we are awake, we are constantly making mental contrasts, or thinking in opposites. For instance, we distinguish black from white, large from small, forwards from backwards, joy from sorrow, and so on, by reason of the fact that the one is the direct opposite of the other. Now, when we are asleep, we sometimes lose this power of contrast, and there occurs in our mind what is called a "unification of opposites" . In other words, we are unable to draw distinctions. When we think we dream of black, it may really be white, up may be down, small may be great, sorrow may signify joy. In fact, almost every dream is a puzzle-picture which must be solved with the aid of past experience.