I search after truth, by which man never yet was harmed.

When men are inhuman, take care not to feel towards them as they do towards other humans.

One of the recurring themes in Marcus' handbook is leadership's responsibility to work intelligently with what it is given and not waste time fantasizing about a world of flawless people and perfect choices.

The true joy of humankind is in doing that which is most proper to our nature; and the first property of people is to be kindly affected towards them that are of one kind with ourselves.

It is within our power not to make a judgement about something, and so not disturb our minds; for nothing in itself possesses the power to form our judgements.

The opinion of 10,000 men is of no value if none of them know anything about the subject.

A man should always have these two rules in readiness. First, to do only what the reason of your ruling and legislating faculties suggest for the service of man. Second, to change your opinion whenever anyone at hand sets you right and unsettles you in an opinion, but this change of opinion should come only because you are persuaded that something is just or to the public advantage, not because it appears pleasant or increases your reputation.