Are there any other qualities common to all dreams? I can think of none, but can see differences only, whichever way I look, differences too in every respect—in apparent duration, definiteness, the part played by affects, persistence in the mind, and so forth. This is really not what we should naturally expect in the case of a compulsive attempt, at once meagre and convulsive, to ward off a stimulus. As regards the length of dreams, some are very short, containing only one image, or very few, or a single thought, possibly even a single word; others are peculiarly rich in content, enact entire romances and seem to last a very long time. There are dreams as distinct as actual experiences, so distinct that for some time after waking we do not realize that they were dreams at all; others, which are ineffably faint, shadowy and blurred; in one and the same dream, even, there may be some parts of extraordinary vividness alternating with others so indistinct as to be almost wholly elusive. Again, dreams may be quite consistent or at any rate coherent, or even witty or fantastically beautiful; others again are confused, apparently imbecile, absurd or often absolutely mad. There are dreams which leave us quite cold, others in which every affect makes itself felt, pain to the point of tears, terror so intense as to wake us, amazement, delight, and so on. Most dreams are forgotten soon after waking; or they persist throughout the day, the recollection becoming fainter and more imperfect as the day goes on; others remain so vivid (as, for example, the dreams of childhood) that thirty years later we remember them as clearly as though they were part of a recent experience. Dreams, like people, may make their appearance once and never come back; or the same person may dream the same thing repeatedly, either in the same form or with slight alterations. In short, these scraps of mental activity at night-time have at command an immense repertory, can in fact create everything that by day the mind is capable of—only, it is never the same. One might attempt to account for these diversities in dreams by assuming that they correspond to different intermediate states between sleeping and waking, different levels of imperfect sleep. Very well; but then in proportion as the mind approached the waking state there should be not merely an increase in the value, content, and distinctness of the dream-performance, but also a growing perception that it _is_ a dream; and it ought not to happen that side by side with a clear and sensible element in the dream there is one which is nonsensical or indistinct, followed again by a good piece of work. It is certain that the mind could not vary its depth of sleep so rapidly as that. This explanation therefore does not help; there is in fact no short cut to an answer.