Jihad is an Arabic word that literally means "to exert strength and effort, to use all means in order to accomplish a task". In Islam, there are two basic theological understandings of the word: the "Greater Jihad" and the "Lesser Jihad". The Greater Jihad is the struggle against the lower self, which involves purifying ones heart, doing good, avoiding evil, and making oneself a better person. The Lesser Jihad is an outward struggle, which may involve fighting against oppressors and aggressors who commit injustice. Jihad constitutes a moral principle to struggle against any obstacle that stands in the way of the good. The term jihad is often rendered in English as "Holy War," although this translation is controversial. In its expanded sense, jihad can be fighting the enemies of Islam, as well as adhering to religious teachings, enjoining good, and forbidding evil. The peaceful sense of "efforts towards the moral uplift of society or towards the spread of Islam" can be known as "jihad of the tongue" or "jihad of the pen," as opposed to "jihad of the sword". Throughout Islamic history, wars against non-Muslims, even when motivated by political and secular concerns, were termed jihads to grant them religious legitimacy. However, the Qurʾān explicitly forbids the initiation of war and permits fighting only against actual aggressors. Furthermore, the jurists forbade attacks on civilians and destruction of property, citing statements by the Prophet Muhammad.