And who has not been fascinated also by the sight of the human stream that pours and pulses through the streets of some great metropolis? This, too, has its currents and counter-currents and eddyings,—all strengthening or weakening according to the tide-rise or tide-ebb of the city's sea of toil. But the attraction of the greater spectacle for us is not really the mystery of motion: it is rather the mystery of man. As outside observers we are interested chiefly by the passing forms and faces,—by their intimations of personality, their suggestions of sympathy or repulsion. We soon cease to think about the general flow. For the atoms of the human current are visible to our gaze: we see them walk, and deem their movements sufficiently explained by our own experience of walking. And, nevertheless, the motions of the visible individual are more mysterious than those of the always invisible molecule of water.—I am not forgetting the truth that all forms of motion are ultimately incomprehensible: I am referring only to the fact that our common relative knowledge of motions, which are supposed to depend upon will, is even less than our possible relative knowledge of the behavior of the atoms of a water-current.
Every one who has lived in a great city is aware of certain laws of movement which regulate the flow of population through the more crowded thoroughfares. (We need not for present purposes concern ourselves about the complex middle-currents of the living river, with their thunder of hoofs and wheels: I shall speak of the side-currents only.) On either footpath the crowd naturally divides itself into an upward and a downward stream. All persons going in one direction take the right-hand side; all going in the other direction take the left-hand side. By moving with either one of these two streams you can proceed even quickly; but you cannot walk against it: only a drunken or insane person is likely to attempt such a thing. Between the two currents there is going on, by reason of the pressure, a continual self-displacement of individuals to left and right, alternately,—such a yielding and swerving as might be represented, in a drawing of the double-current, by zigzag medial lines ascending and descending. This constant yielding alone makes progress possible: without it the contrary streams would quickly bring each other to a standstill by lateral pressure. But it is especially where two crowd-streams intersect each other, as at street-angles, that this systematic self-displacement is worthy of study. Everybody observes the phenomenon; but few persons think about it. Whoever really thinks about it will discover that there is a mystery in it,—a mystery which no individual experience can fully explain.
In any thronged street of a great metropolis thousands of people are constantly turning aside to left or right in order to pass each other. Whenever two persons walking in contrary directions come face to face in such a press, one of three things is likely to happen:—Either there is a mutual yielding,—or one makes room for the other,—or else both, in their endeavor to be accommodating, step at once in the same direction, and as quickly repeat the blunder by trying to correct it, and so keep dancing to and fro in each other's way,—until the first to perceive the absurdity of the situation stands still, or until the more irritable actually pushes his vis-à-vis to one side. But these blunders are relatively infrequent: all necessary yielding, as a rule, is done quickly and correctly.
Of course there must be some general law regulating all this self-displacement,—some law in accord with the universal law of motion in the direction of least resistance. You have only to watch any crowded street for half an hour to be convinced of this. But the law is not easily found or formulated: there are puzzles in the phenomenon.
If you study the crowd-movement closely, you will perceive that those encounters in which one person yields to make way for the other are much less common than those in which both parties give way. But a little reflection will convince you that, even in cases of mutual yielding, one person must of necessity yield sooner than the other,—though the difference in time of the impulse-manifestation should be—as it often is—altogether inappreciable. For the sum of character, physical and psychical, cannot be precisely the same in two human beings. No two persons can have exactly equal faculties of perception and will, nor exactly similar qualities of that experience which expresses itself in mental and physical activities. And therefore in every case of apparent mutual yielding, the yielding must really be successive, not simultaneous. Now although what we might here call the "personal equation" proves that in every case of mutual yielding one individual necessarily yields sooner than the other, it does not at all explain the mystery of the individual impulse in cases where the yielding is not mutual;—it does not explain why you feel at one time that you are about to make your vis-à-vis give place, and feel at another time that you must yourself give place. What originates the feeling?
A friend once attempted to answer this question by the ingenious theory of a sort of eye-duel between every two persons coming face to face in a street-throng; but I feel sure that his theory could account for the psychological facts in scarcely half-a-dozen of a thousand such encounters. The greater number of people hurrying by each other in a dense press rarely observe faces: only the disinterested idler has time for that. Hundreds actually pass along the street with their eyes fixed upon the pavement. Certainly it is not the man in a hurry who can guide himself by ocular snap-shot views of physiognomy;—he is usually absorbed in his own thoughts.... I have studied my own case repeatedly. While in a crowd I seldom look at faces; but without any conscious observation I am always able to tell when I should give way, or when my vis-à-vis is going to save me that trouble. My knowledge is certainly intuitive—a mere knowledge of feeling; and I know not with what to compare it except that blind faculty by which, in absolute darkness, one becomes aware of the proximity of bulky objects without touching them. And my intuition is almost infallible. If I hesitate to obey it, a collision is the invariable consequence.
Furthermore, I find that whenever automatic, or at least semi-conscious, action is replaced by reasoned action—in plainer words, whenever I begin to think about my movements—I always blunder. It is only while I am thinking of other matters,—only while I am acting almost automatically,—that I can thread a dense crowd with ease. Indeed, my personal experience has convinced me that what pilots one quickly and safely through a thick press is not conscious observation at all, but unreasoning, intuitive perception. Now intuitive action of any kind represents inherited knowledge, the experience of past lives,—in this case the experience of past lives incalculable.