It is a tradition in psychology that the comparison of present with past experience implies the arousal of an _image_; we revive or reproduce the old, and then set its mental picture alongside the new. We have met a like tradition before, in our account of recognition and of expectation (pp. 184, 273). Nothing, however, can be more certain than that _the image is unnecessary; comparison may be direct, the immediate outcome of a determination; and if it is indirect, the processes involved need not be images_. Suppose, for instance, that you are comparing two tones, sounded in succession, and that you are to report upon their pitch; you are to say whether the second tone is higher or lower than the first, or of the same pitch. In very many cases, the second tone will evoke, at once and automatically, the report ‘higher,’ ‘lower,’ or ‘same’; you find yourself uttering the word, without further experience of any kind; the whole procedure closes in on itself, very much as the impulse does in the motor reaction (p. 241). In many cases, again, the comparison will be indirect, but the intervening processes are sensations; strains appear in chest or throat, in forehead or scalp; the observers report a ‘tightening’ which means ‘higher,’ and a ‘relaxing’ or ‘slackening’ which means that the second tone is lower. We may suppose that these kinæsthetic processes are empathic; for in playing or singing or listening to music we are likely to strain and hold the breath for high-pitched passages, and to relax and settle down for the low. Lastly, some imaginal complex may intervene; but even so it need not be auditory; the observer may picture a printed score or the piano keyboard, or may feel himself striking a note which is a semitone above or below another. _The auditory image plays a part in the comparison_ only when the experiment is novel, when the second tone fails to touch off a response, or when there is a conflict of impulses to report; in other words, _only when the observer is hesitant and uncertain_; otherwise, it either fails to appear, or appears and is disregarded.