In the 1400s, European exploration was possible because of the previous technological innovations of all of the following civilizations
except
1.mongol
2.song
3.Islam
4.tang

the lowest among the social higher rank were the working class. this class remained detached to the political progression   of the country and was hostile to the other two classes

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.