You can't blame gravity for falling in love.
A ship is safe at shore but it's not built for that.
The one who walks alone, is likely to find himself in places no one has ever been.
It is harder to crack prejudice than an atom.
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.
Playfullness is the essential feature of productive thought.