Sentence:  The concept of <WSD>unity</WSD> , in which positive and negative are attributes of the same force , in which good and evil are relative , ever-changing , and always joined to the same phenomenon - such a concept is still reserved to the physical sciences and to the few who have grasped the history of ideas . 
Meaning of the word marked with <WSD> tags:  an undivided or unbroken completeness or totality with nothing wanting