爱
Three passions， simple but overwhelmingly strong， have governed my life: the longing for love， the search for knowledge， and unbearable pity for the suffering of mankind.
The good life is one inspired by love and guided by knowledge.
It is not a lack of love，but a lack of friendship that makes unhappy marriages.
A sense of duty is just love of one's duty.
True happiness comes from love for oneself and others.
Love takes up where knowledge leaves off.
The things that we love tell us what we are.
The study of truth requires a considerable effort - which is why few are willing to undertake it out of love of knowledge - despite the fact that God has implanted a natural appetite for such knowledge in the minds of men.
The things that we love tell us what we are.