A true friend is a sort of second self.

It is the character of a brave and resolute man not to be ruffled by adversity and not to desert his post.

Fear is not a lasting teacher of duty.

In a discussion of this kind our interest should be centered not on the weight of the authority but on the weight of the argument. Indeed the authority of those who set out to teach is often an impediment to those who wish to learn. They cease to use their own judgment and regard as gospel whatever is put forward by their chosen teacher.

The evil implanted in man by nature spreads so imperceptibly, when the habit of wrong-doing is unchecked, that he himself can set no limit to his shamelessness.

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.

The mere act of believing that some wrongful course of action constitutes an advantage is pernicious.