Good and evil, life and death, selfishness and selflessness, black and white, are they two conflicting concepts or by nature necessary components of a single entity?

They’re not separate, but parts of a unified & coexist reality. 

Art should envelop all of human virtues and vices, beauty and ugliness, strength and weakness. When one fails to express the fullness of its own nature, what is truly inside cannot be fully shined.