zhǐ​zhī​qí​yī​bù​zhī​qí'èr

to know the first, but not the second

只知其一,不知其二 zhǐ​zhī​qí​yī​bù​zhī​qí'èr
to know the first, but not the second
To know only one side of something without knowing the other; describes having an incomplete understanding of a situation or seeing a problem from a one-sided perspective