The great practical difference between the word, written or spoken, and the visual image is that we cannot read the former unless we have been initiated into the mystery of language, whereas visual images can be made intelligible to all men who have eyes.... The spiritual difference between the written word and the visual image is equally great. Precise though a word is, evocative though it be, the actual machinery of visual perception is not engaged. All that takes place, takes place now within the mind; the retina and the neurons sleep; we are in a world which has been created by old, long-stored stimuli; the accidents of energy exterior to ourselves have been totally excluded from it. Even the spoken word is further from this spiritual purity than the word upon the page, for sounds have at least a sensual immediacy of a sort, but the written word is only the ghost of a sound. We have entered now into a realm not of images but of substitutes.