The most essential characteristic of scientific technique is that it proceeds from experiment, not from tradition. The experimental habit of mind is a difficult one for most people to maintain; indeed, the science of one generation has already become the tradition of the next
Diversity is essential to happiness and in Utopia there is hardly any. This is a defect in all planned social systems.
To be able to concentrate for a considerable time is essential to difficult achievement.
I must, before I die, find some way to say the essential thing that is in me, that I have never said yet -- a thing that is not love or hate or pity or scorn, but the very breath of life, fierce and coming from far away, bringing into human life the vastness and the fearful passionless force of non-human things.
Not to be absolutely certain is, I think, one of the essential things in rationality.
It is essential to happiness that our way of living should spring from our own deep impulses and not from the accidental tastes and desires of those who happen to be our neighbors, or even our relations.