This fact was fully recognized by Aristotle, who raised the question why tones are so much more expressive than colors. Music is almost the sole important art that relies on the expressiveness of the sense material alone, independent of any element of meaning. To be sure, the beauty of oriental rugs depends entirely on their color and line harmonies; for the meanings which the patterns have for their oriental makers is generally unknown to us of the western world; yet what we feel when we contemplate them cannot compare in volume and intensity with what we experience when we listen to music. And Aristotle correctly assigned one of the chief reasons for the superior significance of music--its temporal character. A color or line scheme may express a momentary mood, with perhaps just the most rudimentary movement as we go from the dark to the bright colors, or as we follow the motion of the lines as they curve or converge; yet it cannot express an action or process that begins, proceeds, continues, ends. When we look at the colors or lines of a painting or rug, we feel intensely, but there is no development or process of feeling; if the mind moves, it moves inevitably not with, but away from, what it sees. But tones are given to us in succession; we are forced to move with them; hence they come to express for us, in ways which we shall try to analyze, the changing and developing process of the inner life. In its temporal aspect, music has two chief characteristics, rhythm and melody. In our music these are inseparable; yet they can be separated for the purposes of analysis; and a rhythmical roll of drumbeats or a careless succession of tones harmonically related proves that each may produce an aesthetic effect without the other. We shall consider melody first.