Apparently that is not so cut and dry. According to wikipedia (http://en.wikipedia.org/wiki/Standing_on_the_shoulders_of_giants#References_during_the_sixteenth_

Apparently that is not so cut and dry. According to wikipedia (http://en.wikipedia.org/wiki/Standing_on_the_shoulders_of_giants#References_during_the_sixteenth_to_nineteenth_centuries http://en.wikipedia.org/wiki/Standing_on_the_shoulders_of_gi...), the letter with this statement was written at a time when they were on good terms.