In many cases the psychological principle of association operates. The tender expressiveness of certain curved lines, like those of the Greek amphora, for example, is due, partially at least, to association with lines of the human body, with which normally this feeling is associated. The associated object, together with its feeling tone, are sufficiently common to the experience of all men to account for the universality of the emotion, and the isolation of the stimulus--abstract line--from its usual context of color and bulk accounts for the vagueness. Sometimes, on the other hand, expressiveness seems to be due to a direct psychological relation between the sense-stimulus and the emotion. This is almost certainly the case with rhythms, and, as I shall argue in the chapters on painting and music, is at least partially true of colors and tones. The expressiveness is at once too immediate and too universal to depend upon association with definite things and events, or personal, emotional crises. A rhythm, for example, may be exciting the first time it is heard; one does not have to wait to hear it at a battle-charge; a melody may be sad even when one has never heard it sung by chance at parting. Of course the fact that associations are not remembered is no proof that they do not operate; but it is difficult to conceive of any which could operate in these cases. For this reason, I think, we must suppose that certain sense-stimuli and combinations of stimuli not only produce in the sensory areas of the brain the appropriate sensations, but that their effects are prolonged, overflowing into the motor channels and there causing a total reaction of the organism, the conscious aspect of which is a vague feeling. The organic resonance is too slight and diffuse to produce a true emotion; hence only a mood results. In all the representative arts the vague expressiveness of the medium is reinforced through emotions aroused by ideas which interpret sensation as an element of a thing. The green in the painting is not only green, but green of the sea; the red is not only red, but red of the sky; the curved line is not a mere curve, it is the outline of a wave. The totality of colors and lines is not a mere color and line composition, but a marine landscape. The feeling tones of the elements of this complex and of the complex itself are not only those of the colors and lines as such, but of the interpretative ideas as well; which in turn are the same as those of the corresponding real things. The psychological process is here simple enough. The feeling tone of the sea is carried by the idea of the sea, which now fuses with the green color and wavy lines of the painting.