There is a scientific explanation, which it does not matter to give here. Perhaps it may best be understood by the familiar analogy of gout, a complaint that we see produced equally by over-richness or by penury of blood (opposite conditions of blood producing almost the same effect) as in the case of the different parts of the sleepers brain almost opposite results come from the same condition of the circulation. As the circulation to the outer, the peripheral, nerves is lowered during sleep, the senses with which they communicate become less active.

So when a man falls asleep he is in this condition so far as his mental processes are concerned: his reasoning power (which we may take to include will and judgment, and so on, different psychologists have such different divisions, all purely for convenience sake really, of these faculties) and his attention are practically gone, they are comatose, they are fast asleep, whereas his imagination is abnormally active and wide-awake, and his senses are in the condition of semi-activity in which we find them when we begin to "come to" after a dose of anaesthetic. That seems to be a not unfair account of the condition of the sleeper, only - this is important to remember in considering the dream question - he did not go to sleep with his mind in the condition of a tabula rasa. It was not vacant. It was occupied with something. It is not as if the sleeper crossed a line when he fell asleep, and left all his previous chain of connected thought behind him on the other side of the line. It is hard to say that there is any hard and fast line of the kind, and in any case it is quite certain that if there be the mind goes on making its chain, link by link, as the sleeper crosses the line.

In fact we may say that from birth to death (and for aught we know both before birth and after death) we all are forging our life-long chain of associated ideas without a break. A break of course there is, in the shape of a new starting-point, now and again, when the chain is interrupted by some object striking the senses which breaks off the association, and starts a new line of thought; but, if we are to carry the metaphor on, these points of departure would be better marked by some difference in the link - say by an iron ring instead of the ordinary link - in the one long chain, rather than by a new chain altogether.

I can quite well imagine that it will occur to some one to ask me, seeing that I have jumbled up will and judgment (these are not always entirely, but generally and always in some great degree, in abeyance in •dreams) together under the head of reasoning, why I should have bothered to keep "attention" separate. It will be seen, I think, that attention is sometimes present in dreams, so that we look on at and are conscious of ourselves dreaming, while the other higher reasoning faculties are quite in abeyance, and also that the faculty of attention is sometimes quite in abeyance even in some waking states, as, for instance, in the state of reverie (name derived from the dream, the reve, as being so like it) when we pursue a train of thought quite unconsciously, and only when " recalled to ourselves," as we say - that is, when our attention is drawn to what we are doing - do we realise our mental action.

The two ways in which the lengthy chain of lifelong thought is forged prevail in our sleeping mental operations no less than in our waking ones, that is to say there is: (a) the association of ideas working on and on indefinitely until it is interrupted by (6) the appearance of some object of sense that either mingles

■ itself with the previous series of ideas and impressions or starts a new series. These interruptions occur less often in sleep than in the waking state for many obvious reasons - usually we sleep in quiet, in the dark, in the absence of objects to strike the senses; and also the nerves that communicate with the senses are in a state of lowered sensibility, owing to the slower circulation. All this gives the "other way," as the cooks say, a more free chance, and the reasoning faculty, that would tell us when the association of ideas is leading us to impossibilities, being in abeyance, our mind wanders on from absurdity to absurdity of imaginative conception that is not matched in all the thousand and one Arabian Nights. Some of the writers, and Maury, I think, among them, divide the " central" incitements to dreaming into two heads. By "central" incitement, it should be said, is meant the incitement - the starting off - of a dream in the brain itself. Thus any dream arising from the association of ideas would be said to be started from a central incitement. But they also invent another kind of central incitement, in form of some physically suggested thought.

Such a thing may occur, but it is not very easy to see, in the first place, how the people know that the dream started from an accidental physical change in the brain rather than elsewhere; nor, secondly, what special advantage or convenience is gained by distinguishing a dream starting from a sensational cause in the brain itself from a dream starting from any other sensational cause. The useful division to make seems to be between the dream operation that is a simple continuation of the chain of associated ideas and impressions and the dream that is started or modified by some object appealing to one or other of the nerves. This simple division covers all the ground, and it is not easy to see the advantage of complicating it Hartley, indeed, makes a third heading or class, under which he puts ideas and impressions lately received among the originating causes of dreams, but it is evident that these fall under the head of association of ideas and impressions. Maury's theory of associated fibres in the brain spontaneously suggesting impressions is too subtle for us here. The appeal to our senses need not, of course, come from any outward object.