After the ancient world, the concept of otherness, an exclusionary notion of the outside by societies with more or less coherent cultural boundaries, became associated with the development of the monotheistic and prophetic religions of Judaism, Christianity, and Islam (cf.
[16] Moreover, some translations of the Bible, including the King James Version, which is still in vogue today, employ the word infidel, while others have supplanted the term with nonbeliever.
—1 Timothy 5:8 KJVIn Quod super his, Innocent IV asked the question, "[I]s it licit to invade a land that infidels possess or which belongs to them?"
[19] In the extreme, the hierocractic canonical discourse of the mid-twelfth century, such as that espoused by Bernard of Clairvaux, the mystic leader of the Cisertcians, legitimized German colonial expansion and practice of forceful Christianisation in the Slavic territories as a holy war against the Wends, arguing that infidels should be killed wherever they posed a menace to Christians.
[21] The later development of counterarguments on the validity of Papal authority, the rights of infidels, and the primacy of natural law led to various treatises such as those by Hugo Grotius, John Locke, Immanuel Kant and Thomas Hobbes.
During the Age of Discovery, papal bulls such as Romanus Pontifex and, more importantly, inter caetera (1493), implicitly removed dominium from infidels and granted them to the Spanish Empire and Portugal with the charter of guaranteeing the safety of missionaries.
As independent authorities, they drew up charters for their own colonial missions based on the temporal right for care of infidel souls in language echoing the inter caetera.
The charters and papal bulls would form the legal basis of future negotiations and consideration of claims as title deeds in the emerging law of nations during the period of European colonization.
In Worcester v. Georgia, the court ruled that the Native Tribes were sovereign entities to the extent that the U.S. federal government, and not individual states, had authority over their affairs.
Some philosophers such as Thomas Paine, David Hume, George Holyoake, Charles Bradlaugh, Voltaire and Rousseau earned the label of infidel or freethinkers, both personally and for their respective traditions of thought because of their attacks on religion and opposition to the Church.
[24] In 1793, Immanuel Kant's Religion within the Boundaries of Mere Reason, reflected the Enlightenment periods' philosophical development, one which differentiated between the moral and rational and substituted rational/irrational for the original true believer/infidel distinction.
[23] Later during the Victorian era, testimony of either self-declared, or those accused of being Infidels or Atheists, was not accepted in a court of law because it was felt that they had no moral imperative to not lie under oath because they did not believe in God, or Heaven and Hell.
[23] One Arabic language analogue to infidel, referring to non-Muslims, is kafir (sometimes "kaafir", "kufr" or "kuffar") from the root K-F-R, which connotes covering or concealing.
[44][45][46] The class of kafir also includes the category of murtadd, variously translated as apostate or renegades, for whom classical jurisprudence prescribes death if they refuse to return to Islam.
[31] In Sufism the term underwent a special development, as in a well-known verse of Abu Sa'id: "So long as belief and unbelief are not perfectly equal, no man can be a true Muslim", which has prompted various explanations.