Sentence:  An Extravert can hardly conceive the necessity which compels the <WSD>Introvert</WSD> to conquer the world by means of a system. 
Meaning of the word marked with <WSD> tags:  An introverted person: one who is considered more thoughtful than social, with a personality more inwardly than outwardly directed; one who often prefers to have time in non-social situations.