Adam Smith On the Theory of Moral Sentiment
Part III Of Duty
...qand in the same manner, we either aprove or disapprove of our own conduct, according as we feel that, when we place ourselves in the situation of another man, and view it, as it were, with his eyes and from his station, we either can or cannot entirely enter into and sympathize with the sentiments and motives which influenced it.
Were it possible that a human creature could grow up to manhood in some solitary place, without any communication with his own species, he could no more think of his own character, of the propriety or demerit of his own sentiments and conduct, of the beauty or deformity of his own mind, than of the beauty or deformity of his own face. All these are objects which he cannot easily see, which naturally he does not look at, and with regard to which he is provided with no mirror which can present them to his view. Bring him into society, and he is immediately provided with the mirrow which he wanted before. It is placed in the countenance and behaviour of those he lives with, which always marke when they enter into, and when they disapprove of his sentiments.
Our first ideas of personal beauty and defrmity, are drawn from the shape and appearance of others, not from our own. We soon become sensible, however, that others exercise the same criticism upon us. We are pleased when they approve of our figure, and are disobliged when they seem to be disgusted. We become anxious to know how far our appearance deserves either their blame or approbation.
We suppose ourselves the spectators of our own behaviour, and endeavour to imagine what effect it would, in this light, produce upon us. This is the only looking glass by which e can, in some measure, with the eyes of other people, scrutinize the propriety of our own conduct.