Avarice, ambition, vanity, and all passions vulgarly, though improperly, comprized under the denomination of self-love, are here excluded from our theory concerning the origin of morals, not because they are too weak, but because they have not a proper direction, for that purpose. The notion of morals, implies some sentiment common to all mankind, which recommends the same object to general approbation, and makes every man, or most men, agree in the same opinion or decision concerning it. It also implies some sentiment, so universal and comprehensive as to extend to all mankind, and render the actions and conduct, even of the persons the most remote, an object of applause or censure, according as they agree or disagree with that rule of right which is established. These two requisite circumstances belong alone to the sentiment of humanity here insisted on. The other passions produce, in every breast, many strong sentiments of desire and aversion, affection and hatred; but these neither are felt so much in common, nor are so comprehensive, as to be the foundation of any general system and established theory of blame or approbation.
Enquiry Concerning the Principles of Morals, Section IX, Part I.