Susan B Anthony and Elizabeth Cady Stanton's differences helped their cause by showing, by their very existence, that middle ground can be reached between differing ideals. That women may put aside their differences in favor of the movement thus allowing for a greater impact.
A modifier is a word, phrase, or clause that modifies—that is, gives information about—another word in the same sentence. The word <em>small </em>giving information about the noun "park".