What follows is written by the philosopher Bertrand Russell:
Those who realize the harm that can be done to others by any use of force against them, and the worthlessness of the goods that can be acquired by force, will be very full of respect for the liberty of others; they will not try to bind them or fetter them; they will be slow to judge and swift to sympathize; they will treat every human being with a kind of tenderness, because the principle of good in him is at once fragile and infinitely precious.
I'm not sure if I know the exact meaning of "the principle of good" here. Also I would like to know what the role of "of" is in this phrase. (In other words, I'd like to know what the meaning of 'principle' and 'good' are in this context, and what role 'of' is playing here.)