"Some cultures are prosperous; some are not. Some value rational 
discourse and the scientific method; some do not. Some encourage freedom of 
expression, and some discourage it. The only thing they have in common is that 
if they do not propagate, they will be swallowed up by others. All they have 
built up will be torn down; all they have accomplished will be forgotten; all 
they have learned and written will be scattered to the wind. In the old days it 
was easy to remember this because of the constant necessity of border defence. 
Nowadays, it is all too easily forgotten.