Man is by nature competitive, combative, ambitious, jealous, envious, and vengeful.

The course of human history is determined, not by what happens in the skies, but what takes place in our hearts.

The main force used in the evolving world of humanity has hitherto been applied in the form of war.

I prize the conditions under which I have lived because they have permitted me to choose my opportunities, to inquire into such matters as interested me, and to publish what I believed to be true, uncontrolled by any central authority.

In a tribal organization, even in time of peace, service to tribe or state predominates over all self seeking; in war, service for the tribe or state becomes supreme, and personal liberty is suspended.

Reason has not tamed desire: it is as strong as ever.

Whichever theory we adopt to give a rational explanation of human existence, that theory must take into account and explain the mental nature we see at work in all modern communities.