It will be recalled that our main proposition had two sides. One of them has now been dealt with: namely, that physical things do not influence mind (or form ideas and beliefs) except as they are implicated in action for prospective consequences. The other point is persons modify one another's dispositions only through the special use they make of physical conditions. Consider first the case of so-called expressive movements to which others are sensitive; blushing, smiling, frowning, clinching of fists, natural gestures of all kinds. In themselves, these are not expressive. They are organic parts of a person's attitude. One does not blush to show modesty or embarrassment to others, but because the capillary circulation alters in response to stimuli. But others use the blush, or a slightly perceptible tightening of the muscles of a person with whom they are associated, as a sign of the state in which that person finds himself, and as an indication of what course to pursue. The frown signifies an imminent rebuke for which one must prepare, or an uncertainty and hesitation which one must, if possible, remove by saying or doing something to restore confidence. A man at some distance is waving his arms wildly. One has only to preserve an attitude of detached indifference, and the motions of the other person will be on the level of any remote physical change which we happen to note. If we have no concern or interest, the waving of the arms is as meaningless to us as the gyrations of the arms of a windmill. But if interest is aroused, we begin to participate. We refer his action to something we are doing ourselves or that we should do. We have to judge the meaning of his act in order to decide what to do. Is he beckoning for help? Is he warning us of an explosion to be set off, against which we should guard ourselves? In one case, his action means to run toward him; in the other case, to run away. In any case, it is the change he effects in the physical environment which is a sign to us of how we should conduct ourselves. Our action is socially controlled because we endeavor to refer what we are to do to the same situation in which he is acting.