The rule of friendship means there should be mutual sympathy between them, each supplying what the other lacks and trying to benefit the other, always using friendly and sincere words.
Vicious habits are so great a stain to human nature, and so odious in themselves, that every person actuated by right reason would avoid them, though he were sure they would be always concealed both from God and man, and had no future punishment entailed upon them.
There is in fact a true law namely right reason, which is in accordance with nature, applies to all men and is unchangeable and eternal. ... It will not lay down one rule at Rome and another at Athens, nor will it be one rule today and another tomorrow. But there will be one law eternal and unchangeable binding all times and upon all peoples.