The 'Theory of the Moral Sentiments' is a work of great extent and elaboration. It is divided into five Parts; each part being again divided into Sections, and these subdivided into Chapters. PART I. is entitled, OF THE PROPRIETY OF ACTION. _Section I._ is, _'Of the Sense of Propriety.'_ Propriety is his word for Rectitude or Right. Chapter I., entitled, 'Of Sympathy,' is a felicitous illustration of the general nature and workings of Sympathy. He calls in the experience of all mankind to attest the existence of our sympathetic impulses. He shows through what medium sympathy operates; namely, by our placing ourselves in the situation of the other party, and imagining what we should feel in that case. He produces the most notable examples of the impressions made on us by our witnessing the actions, the pleasurable and the painful expression of others; effects extending even to fictitious representations. He then remarks that, although on some occasions, we take on simply and purely the feelings manifested in our presence,--the grief or joy of another man, yet this is far from the universal case: a display of angry passion may produce in us hostility and disgust; but this very result may be owing to our sympathy for the person likely to suffer from the anger. So our sympathy for grief or for joy is imperfect until we know the cause, and may be entirely suppressed. We take the whole situation into view, as well as the expression of the feeling. Hence we often feel for another person what that person does not feel for himself; we act out our own view of the situation, not his. We feel for the insane what they do not feel; we sympathize even with the dead. Chapter II. is 'Of the Pleasure of Mutual Sympathy.' It contains illustrations of the delight that we experience in the sympathy of others; we being thereby strengthened in our pleasures and relieved in our miseries. He observes that we demand this sympathy more urgently for our painful emotions than for such as are pleasurable; we are especially intolerant of the omission of our friends to join in our resentments. On the other hand, we feel pleasure in the act of sympathizing, and find in that a compensation for the pain that the sight of pain gives us. Still, this pleasure may be marred if the other party's own expression of grief or of joy is beyond what we think suitable to the situation. Chapter III. considers 'the manner of our judging of the propriety of other men's affections by their consonance with our own,' The author illustrates the obvious remark, that we approve of the passions of another, if they are such as we ourselves should feel in the same situation. We require that a man's expression and conduct should be suitable to the occasion, according to our own standard of judging, namely, our own procedure in such cases.