Henry Buckle in the history of civilisation

It is evident that until doubt began. progress was impossible. For as we have clearly seen, the advance of civilization solely depends on the acquisitions made by the human intellect and on to the extent to which those acquisitions are diffused.

But men who are perfectly satisfied with their own knowledge will never attempt to increase it. Men who are perfectly convinced of the accuracy of their opinions will never take the pains of examining the basis on which they are built. 

They look with wonder and often with horror, on views contrary to those which they inherited from their fathers; and while they are in this state of mind, it is impossible that they should receive any new truth which interferes with their forgone conclusions.

~ Henry Thomas Buckle