"Les homes construisent trop de murs et pas assez de ponts." (Men build too many walls and not enough bridges.)

Commonly attributed to Isaac Newton and usually presented as "we built too many walls and not enough bridges". 

As even a cursory knowledge of Isaac Newton's thinking would suggest, this is most unlikely to be something he said. 

Indeed it is a recent, and erroneous, attribution. Dominique Pire attributes the quotation to Isaac Newton upon receiving the Nobel Peace Prize in 1958. Earlier attributions do not exist. It seems that Pire confused Isaac Newton with another, less famous, Newton. 

The real author was Joseph Fort Newton, a baptist minister and Freemason. He wrote extensively on Masonry and his actual quotation (with its subtext from Freemasonry) is:

"People are lonely because they build walls instead of bridges."