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Thats your first mistake then. :) it can't be just good.. Otherwise we would be free from sin, which we are not. For good to exist then evil also has to exist. Without evil we have no way of understanding what is good. Evil is deception.. If you are deceived into thinking that human nature is by default all good then you leave yourself open to deception... Because you will not recognise it for what it is or know how to fight and defeat it.
Goodnessis the root,and the evil inclination because of the whispers of Satan and society

Islam believes that human nature is the love of the good and not evil

Contrary to what you believe in,there is no difference between Satan and man in Christianity