We know not in what directions—directions how definitely predetermined—even physical organisms can vary from the common type. We know not what amount of energy any given plant or animal can absorb and incorporate from earth and air and sun. Still less can we predict or limit the possible variations of the soul, the fulness which it may receive from the World-Soul, its possible heritage of grace and truth. But in genius we can watch at each stage the processes of this celestial nurture. We can imagine the outlook of joyous trustfulness; we can almost seem, with Wordsworth, to remember the child's soul entering into the Kingdom of Heaven. Childhood is genius without capacity; it makes for most of us our best memory of inspiration, and our truest outlook upon the real, which is the ideal, world.

From a greater distance we can watch the inward stir of mighty thought, the same for Æschylus, for Newton, for Virgil;—a stir independent of worldly agitation; like the swing and libration of the tide-wave across the ocean, which takes no note of billow or of storm.

Nay, we can see against the sun "the eagle soaring above the tomb of Plato," and in Paul, as in Plotinus, we can catch that sense of self-fulfilment in self-absorption, of rapture, of deliverance, which the highest minds have bequeathed to us as the heritage of their highest hours.

These our spiritual ancestors are no eccentrics nor degenerates; they have made for us the sanest and most fruitful experiment yet made by man; they have endeavoured to exalt the human race in a way in which it can in truth be exalted; they have drawn on forces which exist, and on a Soul which answers; they have dwelt on those things "by dwelling on which it is," as Plato has it, "that even God is divine."

CHAPTER IV
SLEEP

δλβἱα δ' ἑπαντες αἱσα λυσἱπονον μετανἱσσονται τελευτἁν.
καἱ σὡμα μἑν πἁντων ἑπεται θανἁτὡ περισθενεἱ,
ξὡὁν δ' ἑτι λεἱπεται αἱὡνος εἱδωλον' τὁ γἁρ ἑστι μὁνον
ἑκ θεὡν' εὑδει δἑ πρασσὁντων μελἑων, ἁτἁρ εὑδὁντεσσιν ἑν πολλοἱς ὁνεἱροις
δεἱκνυσι τερπνὡν ἑφἑρποισαν χαλεπὡν τε κρἱσιν.
—PINDAR.

THE preceding chapters have carried us two steps upon our way. In Chapter II. we gained some insight into the structure of human personality by analysing some of the accidents to which it is subject; in the third chapter we viewed this personality in its normal waking state, and considered how that norm should be defined, and in what manner certain fortunate persons had integrated the personality still further by utilising uprushes of subliminal faculty to supplement or to crystallise the products of supraliminal thought.

The review of these two chapters indicates clearly enough what my next step must be. It is obvious that in my review of phases or alternations of personality I have left out of sight the most constant, the most important alternation of all. I have thus far said nothing of sleep. Yet that change of personality, at least, has been borne in on every one's notice;—not, certainly, as a morbid curiosity, but as an essential part of life.

Let us then consider the specific characteristics of sleep. The definition of sleep is an acknowledged crux in physiology. And I would point out that the increased experience of hypnotic sleep which recent years have afforded has made this difficulty even more striking than before. A physiological explanation must needs assume that some special bodily condition,—such, for instance, as the clogging of the brain by waste-products,—is at least the usual antecedent of sound sleep. But it is certain, on the other hand, that with a large percentage of persons profound and prolonged sleep can be induced, in any bodily condition, by simple suggestion. Hypnosis, indeed (as Wetterstrand and others have shown) may be prolonged, with actual benefit to the sleeper, far beyond the point which the spontaneous sleep of a healthy subject ever reaches. A good subject can be awakened and thrown into hypnosis again almost at pleasure, and independently of any state either of nutrition or of fatigue. Such sleep belongs to those phenomena which we may call nervous if we will, but which we can observe or influence from the psychological side alone.

We can hardly hope, from the ordinary data, to arrive at a definition of sleep more satisfactory than others have reached. We must defer that attempt until we have collected something more than the ordinary evidence as to what occurs or does not occur during the abeyance of waking life. One point, however, is plain at once. We cannot treat sleep,—as it has generally been treated,—in its purely negative aspect. We cannot be content merely to dwell, with the common text-books, on the mere absence of waking faculties;—on the diminution of external perception, the absence of controlling intelligence. We must treat sleep positively, so far as we can, as a definite phase of our personality, co-ordinate with the waking phase. Each phase, as I believe, has been differentiated alike from a primitive indifference;—from a condition of lowly organisms which merited the name neither of sleep nor of waking. Nay, if there were to be a contest as to which state should be deemed primary and which secondary, sleep might put forward its claim to be regarded as the more primitive phase. It is sleep rather than vigilance which prenatal and infantile life suggest; and even for us adults, however much we may associate ourselves in thought with the waking state alone, that state has at least thus much of secondary and adventitious that it is maintained for short periods only, which we cannot artificially lengthen, being plainly unable to sustain itself without frequent recourse to that fuller influx of vitality which slumber brings.