The state exists for man, not man for the state. The same may be said of science. These are old phrases, coined by people who saw in human individuality the highest human value. I would hesitate to repeat them, were it not for the ever recurring danger that they may be forgotten, especially in these days of organization and stereotypes.
On the left-hand side of the field equation we may add the fundamental tensor guv, multiplied by a universal constant, -λ, at present unknown, without destroying the general covariance.
Nothing truly valuable arises from ambition or from a mere sense of duty; it stems rather from love and devotion towards men and towards objective things.
Common sense invents and constructs no less than its own field than science does in its domain. It is, however, in the nature of common sense not to be aware of this situation.