In simple terms, the good is that which helps people, heals or nourishes or improves or protects them, while evil is that which hurts people. This is simply how human convention has categorized things, and logically so. It is vain to argue that people can’t talk like that if there is no God. Obviously they can use language any way they want to. The distinctions being described are real, and human reaction to those distinctions is naturally explicable.
