[When thinking about the new relativity and quantum theories] I have felt a homesickness for the paths of physical science where there are ore or less discernible handrails to keep us from the worst morasses of foolishness.

For the truth of the conclusions of physical science, observation is the supreme Court of Appeal.

Philosophically, the notion of a beginning of the present order of Nature is repugnant to me ... I should like to find a genuine loophole.

If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations - then so much the worse for Maxwell's equations. If it is found to be contradicted by observation - well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

An ocean traveler has even more vividly the impression that the ocean is made of waves than that it is made of water.

We have found that where science has progressed the farthest, the mind has but regained from nature that which the mind has put into nature. We have found a strange foot-print on the shores of the unknown. We have devised profound theories, one after another, to account for its origin. At last, we have succeeded in reconstructing the creature that made the foot-print. And Lo! it is our own.

In any attempt to bridge the domains of experience belonging to the spiritual and physical sides of nature, time occupies the key position.