1. Purpose of using good and evil
A human being does a wide variety of acts. Judging by right and wrong or accepting the judgement is also one of his/her conducts.
When you see someone who is doing any act and you want to know the meaning of his/her behaviour, what sort of things do you consider?
At first, you will normally think of the actor's motive/purpose, wouldn't you?
For example, if there is a house wife selecting onions and you want to know the meaning of her act, then you will think of her motive/purpose.
In other words, you wonder whether she will cook soup or salad with the onions.
You, of course, won't think about what the onions are thinking or what their purpose of being selected is.
This is because the onions are not the ones who act but they are only objects which exist on the side of being classified.