actuall knowledge ---------our thinking.

Bbase A on/upon B,将A建立在B的基础上base thinking on/upon knowledge将思想建立在知识的基础上knowledge带的是一个定语从句,which to base our thinking upon。为了强调介词与先行词的关系,或习惯问题,将介词upon提前变成upon which to base our thinking。这道题没写完整吧,这里只有knowledge +一个定语从句。