The scientific imagination always restrains itself within the limits of probability.
It is far better for a man to go wrong in freedom than to go right in chains.
There is the greatest practical benefit in making a few failures early in life.
My business is to teach my aspirations to confirm themselves to fact, not to try and make facts harmonize with my aspirations.
Time, whose tooth gnaws away everything else, is powerless against truth.
The rung of a ladder was never meant to rest upon, but only to hold a man's foot long enough to enable him to put the other somewhat higher.