Sentence:  A century ago , Newman saw that liberalism ( what we now might call secularism ) would gradually but definitely make its mark on English Protestantism , and that even high Anglicanism would someday no longer be a `` serviceable breakwater against doctrinal errors more fundamental than its <WSD>own</WSD> '' . 
Meaning of the word marked with <WSD> tags:  belonging to or on behalf of a specified person (especially yourself); preceded by a possessive