The humanity of one man is the humanity of every one
When a man denominates another his ENEMY, his RIVAL, his ANTAGONIST, his ADVERSARY, he is understood to speak the language of self-love, and to express sentiments, peculiar to himself, and arising from his particular circumstances and situation. But when he bestows on any man the epithets of VICIOUS or ODIOUS or DEPRAVED, he then speaks another language, and expresses sentiments, in which he expects all his audience are to concur with him. He must here, therefore, depart from his private and particular situation, and must choose a point of view, common to him with others; he must move some universal principle of the human frame, and touch a string to which all mankind have an accord and symphony. If he mean, therefore, to express that this man possesses qualities, whose tendency is pernicious to society, he has chosen this common point of view, and has touched the principle of humanity, in which every man, in some degree, concurs. While the human heart is compounded of the same elements as at present, it will never be wholly indifferent to public good, nor entirely unaffected with the tendency of characters and manners. And though this affection of humanity may not generally be esteemed so strong as vanity or ambition, yet, being common to all men, it can alone be the foundation of morals, or of any-general system of blame or praise. One man's ambition is not another's ambition, nor will the same event or object satisfy both; but the humanity of one man is the humanity of every one, and the same object touches this passion in all human creatures.
David Hume's Enquiries are the sort of books you should read carefully, marking up fully as you go. It can then be left by a chair or table so that you occasionally sit down next to it and can pick it up and read a paragraph like this one.