“What is morally wrong can never be advantageous, even when it enables you to make some gain that you believe to be to your advantage. The mere act of believing that some wrongful course of action constitutes an advantage is pernicious.”

“Nemo est qui tibi sapientius suadere possit te ipso: numquam labere, si te audies.(Nobody can give you wiser advice than yourself: if you heed yourself, you'll never go wrong.)”

“Six mistakes mankind keeps making century after century:Believing that personal gain is made by crushing others;Worrying about things that cannot be changed or corrected;Insisting that a thing is impossible because we cannot accomplish it;Refusing to set aside trivial preferences;Neglecting development and refinement of the mind;Attempting to compel others to believe and live as we do.”

“Your enemies can kill you, but only your friends can hurt you.”

“As for myself, I can only exhort you to look on Friendship as the most valuable of all human possessions, no other being equally suited to the moral nature of man, or so applicable to every state and circumstance, whether of prosperity or adversity, in which he can possibly be placed. But at the same time I lay it down as a fundamental axiom that "true Friendship can only subsist between those who are animated by the strictest principles of honour and virtue." When I say this, I would not be thought to adopt the sentiments of those speculative moralists who pretend that no man can justly be deemed virtuous who is not arrived at that state of absolute perfection which constitutes, according to their ideas, the character of genuine wisdom. This opinion may appear true, perhaps, in theory, but is altogether inapplicable to any useful purpose of society, as it supposes a degree of virtue to which no mortal was ever capable of rising.”

“So it may well be believed that when I found him taking a complete holiday, with a vast supply of books at command, he had the air of indulging in a literary debauch, if the term may be applied to so honorable an occupation.”

“Never injure a friend, even in jest.”