Today, more than ever before, life must be characterized by a sense of Universal responsibility, not only nation to nation and human to human, but also human to other forms of life.
The day was made for laziness, and lying on one's back in green places, and staring at the sky till its brightness forced one to shut one's eyes and go to sleep.
Mathematics would certainly have not come into existence if one had known from the beginning that there was in nature no exactly straight line, no actual circle, no absolute magnitude.
For us who live in cities Nature is not natural. Nature is supernatural. Just as monks watched and strove to get a glimpse of heaven, so we watch and strive to get a glimpse of earth. It is as if men had cake and wine every day but were sometimes allowed common bread.
It is not necessarily those lands which are the most fertile or most favored in climate that seem to me the happiest, but those in which a long struggle of adaptation between man and his environment has brought out the best qualities of both.
After you have exhausted what there is in business, politics, conviviality, and so on - have found that none of these finally satisfy, or permanently wear - what remains? Nature remains.