Sentence:  When we see the steady and methodical inculcation into humanity of the idea of man 's worthlessness - until redeemed - the <WSD>necessity</WSD> of the Devil may become evident as a weapon , a weapon designed and used time and time again in every age to whip men into a surrender to a particular church or church-state '' . 
Meaning of the word marked with <WSD> tags:  the condition of being essential or indispensable