There is no concept of absolute evil in Islam, as a fundamental universal principle that is independent from and equal with good in a dualistic sense. Although the Quran mentions the biblical forbidden tree, it never refers to it as the 'tree of knowledge of good and evil'. Within Islam, it is considered essential to believe that all comes from God, whether it is perceived as good or bad by individuals; and things that are perceived as "evil" or "bad" are either natural events (natural disasters or illnesses) or caused by humanity's free will. Much more the behavior of beings with free will, then they disobey God's orders, harming others or putting themselves over God or others, is considered to be evil. Evil doesn't necessarily refer to evil as an ontological or moral category, but often to harm or as the intention and consequence of an action, but also to unlawfull actions.