The first element is that of the rhythm of the line with which the forms are delineated.

The drawn line is the record of a gesture, and that gesture is modified by the artist’s feeling which is thus communicated to us directly.

The second element is mass. When an object is so represented that we recognise it as having inertia we feel its power of resisting movement, or communicating its own movement to other bodies, and our imaginative reaction to such an image is governed by our experience of mass in actual life.

The third element is space. The same sized square on two pieces of paper can be made by very simple means to appear to represent either a cube two or three inches high, or a cube of hundreds of feet, and our reaction to it is proportionately changed.

The fourth element is that of light and shade. Our feelings towards the same object become totally different according as we see it strongly illuminated against a black background or dark against light.

A fifth element is that of colour. That this has a direct emotional effect is evident from such words as gay, dull, melancholy in relation to colour.

I would suggest the possibility of another element, though perhaps it is only a compound of mass and space: it is that of the inclination to the eye of a plane, whether it is impending over or leaning away from us.

Now it will be noticed that nearly all these emotional elements of design are connected with essential conditions of our physical existence: rhythm appeals to all the sensations which accompany muscular activity; mass to all the infinite adaptations to the force of gravity which we are forced to make; the spatial judgment is equally profound and universal in its application to life; our feeling about inclined planes is connected with our necessary judgments about the conformation of the earth itself; light, again, is so necessary a condition of our existence that we become intensely sensitive to changes in its intensity. Colour is the only one of our elements which is not of critical or universal importance to life, and its emotional effect is neither so deep nor so clearly determined as the others. It will be seen, then, that the graphic arts arouse emotions in us by playing upon what one may call the overtones of some of our primary physical needs. They have, indeed, this great advantage over poetry, that they can appeal more directly and immediately to the emotional accompaniments of our bare physical existence.

If we represent these various elements in simple diagrammatic terms, this effect upon the emotions is, it must be confessed, very weak. Rhythm of line, for instance, is incomparably weaker in its stimulus of the muscular sense than is rhythm addressed to the ear in music, and such diagrams can at best arouse only faint ghost-like echoes of emotions of differing qualities; but when these emotional elements are combined with the presentation of natural appearances, above all with the appearance of the human body, we find that this effect is indefinitely heightened.

When, for instance, we look at Michelangelo’s “Jeremiah,” and realise the irresistible momentum his movements would have, we experience powerful sentiments of reverence and awe. Or when we look at Michelangelo’s “Tondo” in the Uffizi, and find a group of figures so arranged that the planes have a sequence comparable in breadth and dignity to the mouldings of the earth mounting by clearly-felt gradations to an overtopping summit, innumerable instinctive reactions are brought into play.[3]